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ANATOMY 


PHYSIOLOGY 


A  TEXT-BOOK  FOE  NURSES 


BY 

JOHN  FORSYTH  LITTLE,  Af.L). 

ASSISTANT    DEMONSTRATOR    OF    ANATOMY,    JEFFERSON    MEDICAL    COLLEGE 
PHILADELPHIA 


ILLUSTRATED  WITH   149  ENGRAVINGS  AND 
4  PLATES 


LEA   &   FEBIGER 
PHILADELPHIA   AND    NEW   YORK 

K\X. 


Entered  according  to  the  Act  of  Congress,  in  the  year  1914,  by 

LEA   &   FEBIGER, 
in  the  office  of  the  Librarian  of  Congress.     All  rights  reserved. 


I  V— w 


77 
9l4- 


PREFACE 


In  presenting  this  work  to  the  nursing  profession 
tlie  author  has  endeavored  to  cover  in  as  clear  and 
untechnical  a  manner  as  possible  the  essentials  of 
anatomy  and  physiology.  No  theories  have  been 
included,  except  those  which  have  been  definitely 
accepted  by  teachers  of  the  subjects.  Emphasis  has 
been  placed  on  the  description  of  organs  and  their 
functions  which  are  of  fundamental  importance  in 
the  practice  work  of  the  nurse. 

The  questions  at  the  end  of  each  chapter  are  added 
as  a  means  of  reviewing  the  subjects. 

The  glossary  has  been  added  with  the  object  of 
explaining  all  technical  words  in  the  text. 

J.  F.  L. 


5(;7;) 


J 


CONTENTS 


CHAPTER   I 

Introduction 17 

CHAPTER  II 

Chemic  Composition  of  the  Human  Body    ....       20 

CHAPTER  III 

Metabolism — The  Cell,  its  Stkucture  and  Functions       29 

CHAPTER  IV 

Tissues 35 

CHAPTER  V 

Osteology — The   Description   of   Bones    and    Bone 

Tissue 54 

CHAPTER  VI 

Articulations  or  Joints 106 

CHAPTER  VII 

Muscle  Tissue       ...  - 117 

CHAPTER   VIII 

The  Description  of  the  Anatomy  and  Physiology  of 

the  Circulatory  Apparatus 174 

CHAPTER   IX 
The  Lymphatic  System 225 


vi  CONTENTS 

CHAPTER  X 

The  Respiratory  Apparatus 233 

CHAPTER  XI 

The  Organs  of  Digestion 251 

CHAPTER  XII 

Digestion 275 

CHAPTER  XIII 

Absorption 286 

CHAPTER  XIV 

Secretion 290 

CHAPTER  XV 

The  Factors  Essential  to  the  Production  of  Body 

Temperature  or  Heat 310 

CHAPTER  XVI 

The  Anatomy  and  Physiology  of  the  Urinary  Appar- 
atus (Organs);  the  Skin  and  its  Appendages     .     314 

CHAPTER  XVII 

Anatomy  and  Physiology  of  the  Nerve  System  .      .331 

CHAPTER  XVIII 

The  Organs  of  Special  Sense 390 

CHAPTER  XIX 

Organs  of  Reproduction 417 


ANATOMY  AND  PHYSIOLOGY 


CHAPTER  I 

INTRODUCTION 

The  human  body  from  birth  to  old  age  exhibits  in 
the  living  condition  a  series  of  phenomena  by  which  it 
grows,  performs  the  various  and  complex  movements 
of  which  man  is  capable  in  the  processes  of  daily  life; 
thinks,  and  is  conscious  of  the  sensations  which  bring 
him  into  relation  with  his  surroundings,  and  repro- 
duces, permitting  a  continuation  of  the  species. 

A  study  of  the  functions  of  the  numerous  organs 
and  structures  of  the  body  in  a  state  of  health,  and  their 
associated  phenomena  of  growth,  movement,  mentality, 
and  reproduction,  is  termed  human  physiology. 

To  understand  the  functions  of  organs,  etc.,  it  is 
necessary  to  first  understand  the  construction  of  the 
human  body  of  which  they  are  a  part.  To  this  branch 
of  science  the  term  human  anatomy  is  applied. 

THE  ANATOMIC  ARRANGEMENT  OF  THE  BODY 
AS  A  WHOLE 

The  human  body  is  divided  into  an  axial  portion 
consisting  of  the  head,  neck,  and  trunk;  and  an  appen- 
dicular portion,  including  the  limbs  or  extremities — 
arms,  legs,  etc. 

The  axial  portion  is  subdivided  into  a  posterior  or 
dorsal  cavity,  and  an  anterior  or  ventral  cavity. 

The  dorsal  cavity  is  formed  by  the  vertebrae  and  their 
arches  of  bone,  and  the  bones  of  the  skull.  If  the 
2 


18  INTRODUCTION 

dorsal  cavity  is  sectioned  in  a  longitudinal  direction 
it  will  show,  above,  the  cranial  cavity,  and  below, 
the  spinal  cord,  the  former  containing  the  brain  and 
its  membranes,  the  latter  the  spinal  cord  and  its 
membranes. 

The  ventral  cavity  includes  the  space  within  the 
trunk  and  in  front  of  the  spinal  column.  Its  walls 
consist  of  skin,  fascia,  and  muscles  reinforced  by  bony 
arches,  the  ribs,  and  the  pelvic  bones.  The  ventral  cavity 
is  subdivided  by  a  musculomembranous  wall,  the  dia- 
phragm, into  an  upper  cavity  called  the  thorax,  and  a 
lower  one,  the  abdomen.  The  former  contains  the  organs 
of  respiration — the  lungs  and  the  heart,  covered  by  their 
membranes,  also  the  great  bloodvessels  leading  from 
the  heart,  and  the  esophagus  (gullet),  which  conveys 
food  from  the  pharynx  to  the  stomach  by  passing 
through  the  diaphragm.  The  abdomen  contains  the 
remaining  portions  of  the  tube  (alimentary  canal), 
which  receives  the  food  from  the  esophagus  and  ends 
in  the  lower  part  of  the  cavity  called  the  anus;  also 
the  organs  of  secretion — liver,  pancreas,  spleen,  etc.; 
excretion — kidneys,  bladder,  etc.,  and  reproduction  in 
the  female. 

The  appendicular  portion  of  the  body  consists  of  four 
extremities — two  upper  and  two  lower  limbs.  The 
upper  limbs  consist  of  bones  held  together  by  liga- 
ments, and  covered  with  muscles,  tendons,  fascia,  and 
skin.  The  lower  limbs  have  the  same  construction  as 
the  upper,  but  the  joints  are  not  so  capable  of  move- 
ment. For  example,  the  shoulder  and  elbow  are  freely 
movable,  as  compared  with  the  hip. 

The  study  of  anatomy  is  divided  into  the  following 
branches : 

Osteology:  the  anatomy  of  the  bones. 

Syndesmology :  the  anatomy  of  the  joints. 

Myology:  the  anatomy  of  the  muscles. 

Angiology:  the  anatomy  of  the  bloodvessels. 

Neurology:  the  anatomy  of  the  nerves. 


ANATOMIC  ARRANGEMENT  OF  THE  BODY     19 

Splanchnology:  the  anatomy  of  the  internal  organs 
— digestion,  respiration,  etc. 

The  construction  of  each  organ  and  portion  of  the 
body,  and  its  independent  function,  as  well  as  the 
combined  actions  of  several  organs  entering  into 
the  performance  of  a  definite  act,  as  in  digestion,  etc., 
are  described  under  the  term  physiologic  apparatus. 

Digestive  apparatus,  by  means  of  which  food  isdigested. 
Absorptive  apparatus,  for  the  absorption  of  nourishment 
into  the  lymph  and  blood.  Circulatory  apparatus,  for 
the  distribution  of  blood  from  the  heart  to  all  portions 
of  the  body.  The  respiratory  apparatus,  by  means  of 
which  oxygen  is  absorbed  into  the  blood  from  the  air 
breathed  into  the  lungs,  and  carbon  dioxide  and  other 
waste  materials  are  given  off  from  the  blood  to  the 
atmosphere.  Urinary  apparatus,  for  the  elimination 
of  waste  materials  from  the  body  through  the  kidneys 
and  bladder,  as  urine.  Secretory  and  perspiratory 
apparatuses — the  former  secreting  essential  materials 
for  the  maintenance  of  body  nutrition;  the  latter 
aiding  in  regulating  heat  dissipation  and  in  eliminating 
waste  materials  through  the  sweat  glands  of  the  skin. 

QUESTIONS 

1.  What  do  you  understand  by  the  term  human  physiology? 
Human  anatomy? 

2.  Name  the  two  portions  the  body  is  divided  into, 

3.  Give  the  parts  of  the  body  included  under  the  axial  and  appen- 
dicular portions. 

4.  Name  the  cavities  included  in  the  subdivision  of  the  axial 
portion. 

5.  Describe  the  dorsal  cavity.    Ventral  cavity. 

6.  What  are  the  subdivisions  of  the  dorsal  cavity  and  contents? 

7.  What  are  the  subdivisions  of  the  ventral  cavity? 

8.  Name  the  structure  which  subdivides  the  abdomen  and  thorax. 

9.  What  are  the  principal  organs,  etc.,  contained  in  the  thorax? 
Abdomen? 

10.  How  many  extremities  or  limbs  are  included  under  the  appen- 
dicular portion  of  the  body? 

11.  What  do  you  understand  by  the  following  terms:  Osteology, 
syndesmology,  myology,  angiology,  neurology,  splanchnology? 

12.  What  do  you  understand  by  the  term  physiologic  apparatus? 


CHAPTER  II 

CHEMIC  COMPOSITION  OF  THE  HUMAN 
BODY 

The  human  body  after  a  chemic  analysis  can  be 
reduced  into  its  final  constituents.  The  analysis 
of  the  dead  body  is  completed  with  little  difficulty, 
while  the  analysis  of  the  constituents  of  the  living 
body  is  a  most  complicated  and  arduous  task.  The 
former  procedure  is  called — chemic  anatomy,  while 
the  latter  is  termed  chemiic  physiology. 

The  analysis  of  the  human  body  will  disclose  the 
fact  that  it  contains  liquid  and  solid  compounds  which 
belong  to  both  the  organic  and  inorganic  chemic 
and  plant  w^orld.  These  compounds  derived  from 
a  proximate  analysis  are  termed  proximate  principles. 
However,  to  deserve,  this  term  they  must  be  obtained 
in  the  form  in  which  they  exist  in  the  living  body. 

The  organic  compounds  consist  of  carbohydrates, 
fatty  and  protein  groups  of  organic  bodies;  the 
inorganic  compounds  consist  of  water,  various  acids, 
and  inorganic  salts. 

Chemic  Elements  Foimd  in  the  Human  Body :  Oxygen, 
72  per  cent.;  hydrogen,  9.1;  nitrogen,  2.5;  carbon, 
13.5;  phosphorus,  1.15;  calcium,  1.3;  sulphur,  0.147; 
sodium,  0.1;  potassium,  0.026;  chlorin,  0.085;  fluorin, 
iron,  silicon,  magnesium,  iodine,  in  small  amounts. 

ORGANIC   COMPOUNDS 

The  Carbohydrates. — The  carbohydrates  are  repre- 
sented in  the  human  body  mostly  as  starches  and 
sugars.    They  contain  carbon,  hydrogen,  and  oxygen. 


ORGANIC  COMPOUNDS  21 

but  no^  nitrogen  —  the  hydrogen  and  oxygen  being 
in  such  proportion  as  to  form  water,  or  as  2  to  1, 
as  is  shown  in  the  chemic  formula  for  starch, 
CeHioOs. 

Few  of  the  carbohydrates  are  found  in  the  human 
body,  but  are  found  mostly  in  the  foods  we  eat.  They 
are  the  most  beneficial  nourishment  for  the  mainten- 
ance of  heat  and  energy,  and  are,  besides,  available 
and  easy  of  digestion. 

The  carbohydrates  are  divided  into  three  groups: 
(1)  Amyloses,  including  starch,  dextrin,  glycogen,  and 
cellulose;  (2)  dextroses,  including  dextrose,  levulose, 
galactose;  (3)  saccharoses,  including  saccharose,  lac- 
tose, maltose. 

1.  Amyloses  (CeHioOs),,.^ — Starch  forms  about  10 
per  cent,  of  the  body  weight.  It  is  a  constituent  in 
wheat,  Indian  corn,  oats,  cereals,  plants,  potatoes, 
peas,  beans,  and  some  fruits.  In  the  presence  of  a 
ferment,  such  as  ptyalin — in  the  saliva — starch  is 
converted  into  maltose  and  dextrose,  two  forms  of 
sugar. 

Dextrin  is  a  substance  formed  as  an  intermediary 
product  in  the  change  of  starch  into  dextrose.  It  is 
divided  into  two  varieties — erythrodextrin  and  achro- 
odextrin 

Glycogen,  or  animal  starch,  is  a  constituent  of  the 
animal  liver,  muscles,  and  tissues  generally,  particularly 
the  tissues  of  the  embryo. 

Cellulose  is  found  mostly  in  plants. 

2.  Dextroses  (C6H12O6). — Dextrose,  glucose,  or  grape- 
sugar  occurs  as  irregular,  warty  masses,  usually  as  a 
thick  syrup.  It  is  a  constituent  of  the  vegetable 
kingdom;  generally  found  with  fruit-sugar  or  levulose 
in  fruits,  as  grapes,  peaches,  figs,  cherries,  mulberries, 
strawberries,  etc.  It  is  also  found  in  honey,  and  is 
a  normal  constituent  of  liver,  blood,  and  urine  in  small 
quantities,  in  health,  and  is  an  indication  of  the  disease 
diabetes  mellitus  when  found  in  larger  amounts. 


22     CHE  MIC  COMPOSITION  OF  THE  HUMAN  BODY 

Levulose  or  fruit-sugar  is  associated  with  dextrose  as 
a  constituent  of  sweet  fruits  and  honey. 

Galactose  is  obtained  when  milk-sugar  (lactose)  is 
boiled  with  dilute  sulphuric  acid. 

3.  Saccharoses. — Saccharose  or  cane-sugar  occurs  as 
hard,  crystalline  granules.  It  is  found  in  the  juices  of 
plants;  in  different  grasses  (sugar-cane);  in  the  forest 
trees  (maple-sugar);  and  in  the  roots  and  stems  of 
plants  (beet-sugar),  etc. 

Molasses  is  a  product  derived  from  the  evaporation 
and  refining  of  cane-sugar,  as  is  caramel  or  burnt- 
sugar. 

Maltose  is  formed  from  starch,  when  acted  on  by 
malt  extract  or  the  diastatic  ferments  in  saliva  and 
pancreatic  juice.  The  diastatic  ferment  or  diastase 
is  a  substance  resulting  from  allowing  the  seeds  of 
rye,  wheat,  barley,  etc.,  to  germinate  in  the  manu- 
facture of  alcoholic  liquors.  This  when  formed  acts 
on  the  starch  and  converts  it  into  maltose  and  dextrin. 
Lactose  or  milk-sugar  is  found  only  in  the  milk  of  mam- 
malia. In  the  stomach  of  human  beings,  in  the  pres- 
ence of  the  lactic  acid  bacillus,  it  is  changed  to  lactic 
acid  and  then  to  butyric  acid. 

Fats. — Fats  or  hydrocarbons  are  organic  bodies  found 
in  the  tissues  of  both  vegetables  and  animals.  They 
are  the  most  valuable  food  next  to  the  carbohydrates, 
as  a  source  of  heat  and  energy,  but  are  not  so  available 
or  so  easily  digested.  They  are  found  in  the  subcuta- 
neous tissues,  marrow  of  bones,  in  and  around  the 
numerous  internal  organs,  back  of  the  eye-balls,  the 
omentum,  in  milk;  and  in  very  stout  persons  they  are 
found  in  the  liver,  kidney,  heart  muscle,  and  muscles 
of  the  extremities,  also  along  arteries,  veins,  and 
nerves.  Fat  is  found  in  the  animal  foods,  such  as, 
meat,  fish,  butter;  in  vegetable  foods,  as  oils,  cereals, 
and  in  the  kernels  of  nuts. 

Fats  are  compounds  consisting  of  carbon,  hydrogen 
and    oxygen,    the   first   being   the   main   ingredient, 


ORGANIC  COMPOUNDS  23 

forming>by  weight  about  75  per  cent.,  while  oxygen  is 
present  in  very  small  amounts.  The  fat  found  in 
animals  is  a  mixture  of  three  neutral  fats — stearin, 
palmitin,  and  olein.  Each  fat  is  derived  from  glycerin 
and  the  acid  indicated  by  its  name — e.  g.,  oleic  acid, 
in  the  case  of  olein,  etc. 

When  we  speak  of  saponification  we  mean  that  a  neu- 
tral fat  has  been  treated  with  a  superheated  steam 
or  saponified — i.  e.,  broken  up  into  glycerin  and  a 
fatty  acid,  as  stearic,  oleic,  or  palmitic,  the  resulting 
acid  depending  on  the  neutral  fat  used. 

Soaps. — Soaps  are  formed  when  saponification  takes 
place  in  the  presence  of  an  alkali — e.  g.,  potassium  or 
sodium  hydroxid — the  acid  combines  with  the  alkali 
to  form  a  salt  known  as  soap,  the  glycerin  remaining 
in  solution. 

Soaps  are  salts.  Soaps  made  with  sodium  hydroxid 
are  hard,  those  with  potassium  hydroxid  are  soft. 
Those  derived  from  stearin  and  palmitin  are  harder 
than  those  made  with  olein. 

The  Animal  Fats. — Butter,  cream,  lard,  suet,  oleo- 
margarin,  cottolene,  butterine,  cod-liver  oil,  and 
bone-marrow  are  the  animal  fats  of  the  most  import- 
ance. 

The  Vegetable  Fats. — Those  most  commonly  em- 
ployed are — olive  oil,  cotton-seed  oil,  linseed  oil, 
cocoa-butter,  and  the  oils  derived  from  nuts,  such 
as  cocoanut  oil,  peanut  oil,  and  almond  oil. 

The  Proteins. — Proteins  are  found  in  both  animals 
and  vegetables,  and  contain  most  of  the  nitrogenous 
compounds  essential  for  their  physiologic  needs.  In 
the  former  they  are  found  as  constituents  of  the  blood, 
tissues,  bones,  muscles,  nerves,  glands,  and  all  other 
organs;  in  the  latter,  in  nearly  all  parts  of  plants 
and  seeds.  They  are  represented  in  the  vegetable 
food  which  we  eat,  as  constituents  of  gluten  of  grain, 
etc.;  in  the  animal  food,  as  the  lean  and  gristle  of  beef, 
the  white  of  egg,  casein  of  milk  (the  curd),  etc. 


24     CHEMIC  COMPOSITION  OF  THE  HUMAN  BODY 

Protein  contains  carbon,  hydrogen,  nitrogen,  oxygen, 
sulphur,  and  some  phosphorus.  The  chemic  constit- 
uents, however,  are  so  complex  that  a  definite  chemic 
formula,  representing  each  ingredient,  has  not  been 
satisfactorily  determined.  They  are  the  most  stable 
of  the  constituents  of  the  body,  and  help  to  build  up 
new  tissues  and  replenish  the  quantity  necessary  to 
maintain  the  loss  from  waste  of  the  old,  resulting  from 
the  wear  and  tear  of  daily  existence,  through  work, 
mental  or  physical,  oxidation,  elimination,  etc.  They 
are  also  converted  into  heat  and  energy,  but  are  not 
so  essential  to  the  body  for  the  former  purpose,  as 
the  carbohydrates  or  fats.  They  are  also  converted 
into  fat  and  stored  up  in  the  body  for  future  use. 

The  proteins  and  their  various  tests  and  physical 
properties  are  too  numerous  to  mention  or  discuss, 
especially  as  they  are  not  essential  to  a  nurse's  knowledge. 
I  shall  simply  mention  the  important  ones  or  the  ones 
of  most  interest  as  constituents  of  the  more  familiar 
tissues  and  foods,  under  the  headings  as  follows: 
Albumins,  globulins,  albuminoids. 

Albumins :  Serum-albumin — in  blood,  lymph,  chyle. 
Egg-albumen — in  white  of  egg. 
Lact-albumin — in  milk. 
Myo-albumin — in  plasma  of  muscle. 
Globulins:  Serum-globulins — in  blood  serum. 

Fibrinogen — in  blood  plasma  (with  serum-albumin 

and  globulin). 
Myosinogen — in  muscle  plasma  (very  nutritive). 
Crystallin  or  globulin — in  crystalline  lens  of  eye. 
Albuminoids:  Collagen  and  ossein — in  white  fibrous 
tissue  and  bones. 
Choridrin — in  permanent   cartilage. 
Elastin — in  fibers  of  yellow  elastic  tissue. 
Keratin — in   horny   tissues   and   skin — as   hairs, 

nails,  scales,  horns  of  animals,  etc. 
Caseinogen — in  milk — contains  phosphorus. 
Vitellin — in  yolk  of  egg — contains  phosphorus. 


INORGANIC  COMPOUNDS  25 

Compound  Albuminoids:  Hemoglobin — in  red  cells  of 
blood  (coloring  matter). 
Mucin — in  secretions  of  mucous  membranes  and 

epithelial  cells. 
Nuclein — in  the  nuclei  of  tissue  cells  and  sub- 
stance (rich  in  phosphorus). 

Proteoses  and  Peptones. — These  are  resulting  proteins 
formed  during  digestion  by  the  action  of  the  gastric 
and  pancreatic  juices  upon  the  proteins  as  they  pass 
through  the  process  of  digestion  in  the  stomach  and 
intestines. 

Three  coagulated  proteins  are  formed  when  soluble 
proteins  are  acted  upon  by  animal  ferments,  e.  g., 
fibrin,  myosin,  casein. 

Fibrin. — This  is  formed  from  the  soluble  protein — 
fibrinogen — by  the  action  of  a  special  ferment.  It  is 
not  found  except  when  blood  is  withdrawn  from  the 
vessels  or  when  coagulation  occurs.  Blood-clots  fol- 
lowing hemorrhage,  by  the  action  of  the  ferment  on 
the  fibrinogen,  forming  fibrin. 

Myosin. — ^This  is  a  protein  derived  from  a  soluble 
protein  myosinogen.  It  occurs  in  muscles  after  death 
and  accounts  for  the  stiffness  of  the  limbs — rigor 
mortis. 

Casein. — This  is  formed  as  a  result  of  the  action  of 
a  special  ferment — rennin,  a  constituent  of  the  gastric 
juice — acting  upon  the  protein — caseinogen — of  milk. 
This  is  the  ferment  which  splits  milk  into  curds  and 
whey  or  junket.  Th€  curds  represent  the  solid  por- 
tion or  casein;  the  whey,  the  liquid  portion.  (See 
Digestion.) 

INORGANIC  COMPOUNDS 

Water  (H2O). — Water  is  the  most  important  inor- 
ganic substance  essential  to  life.  It  is  in  the  tissues 
and  fluids  of  the  body,  comprising  75  to  90  per  cent, 
of  its  weight.    In  a  person  weighing  165  pounds,  115 


26     CHE  MIC  COMPOSITION  OF  THE  HUMAN  BODY 

pounds  of  that  weight  will  consist  of  water.  It  enters 
into  the  foods  and  liquids  we  assimilate;  acts  as  a 
solvent  for  the  various  salts,  carbohydrates,  fats, 
proteins,  etc.;  aids  in  the  absorption  of  fresh  material 
into  the  blood  and  tissues;  assists  in  dissolving  and 
transferring  the  products  of  disintegrating  tissues  to 
the  blood  from  which  it  is  eliminated  by  way  of  the 
skin  (perspiration),  kidneys  (urine),  lungs,  and  intes- 
tines (feces). 

The  Inorganic  Salts. — These  are  calcium  phosphate, 
fluorid  and  carbonate;  sodium  chloride,  phosphate, 
carbonate,  and  sulphate;  potassium  chlorid,  phosphate 
and  carbonate;  magnesium  phosphate  and  carbonate. 

Salts  enter  into  the  formation  of  all  tissues  of  the 
body.  Sodium  chlorid — common  table  salt — is  the 
most  important  of  the  group. .  It  is  the  chief  salt 
found  in  the  blood,  lymph,  and  pancreatic  juice. 
As  a  seasoning  for  food,  it  adds  to  its  relish  and  thus 
promotes  digestion.  By  a  chemical  process  it  helps 
to  form  the  hydrochloric  acid,  and  produces  the  alka- 
linity of  the  blood.  Potassium  chlorid  is  found  in 
association  with  sodium  chlorid  throughout  the  tissues, 
and  is  a  chemic  constituent  of  muscle,  nerve,  and  red 
corpuscles.  Calcium  salts  are  found  as  constituents 
of  bones,  teeth,  cartilage,  blood,  milk,  and  other  tis- 
sues. All  of  the  above  combinations  are  to  be  found 
throughout  the  body,  but  their  various  physiologic 
and  chemic  properties  are  not  essential  to  the  nurse's 
knowledge. 

Phosphorus. — Phosphorus  is  found  in  the  muscles, 
bones,  nerve  system,  and  blood,  in  various  chemic 
combinations,  as  phosphates,  also  in  both  animal 
and  vegetable  foods. 

Sulphur. — Sulphur  is  found  in  the  body  in  the  form 
of  sulphates,  which  are  derived  from  egg-albumen, 
milk,  and  certain  vegetables. 

Iron. — Iron  is  an  essential  constituent  of  the  color- 
ing matter  (hemoglobin)   of  the  blood,  lymph,   bile, 


QUESTIONS  27 

gastric  juice,  pigment  of  the  eyes,  hair,  and  skin.  It 
is  found  in  chemic  combination  only,  as  ferric  acid 
and  in  organic  compounds. 

There  are  constituents  of  the  body,  aside  from 
proteins,  fats,  carbohydrates,  and  inorganic  salts, 
which  can  only  be  located  by  the  various  chemic 
analyses  and  tests.  They  are  the  substances  resulting 
from  the  numerous  and  complicated  changes  con- 
tinually taking  place  in  the  food  we  eat  and  water  we 
drink,  as  a  result  of  digestion,  absorption,  etc.  They 
are  carried  to  the  tissues,  where  they  perform  their 
functions,  and  then  are  taken  up  from  the  tissues  by 
the  blood  and  carried  to  the  skin  (as  perspiration), 
kidneys  (as  urine),  lungs  (as  carbon  dioxid),  and  intes- 
tines (as  feces),  to  be  eliminated  as  waste  materials. 
These  substances  are:  (1)  Organic  acids,  e.  g.,  acetic, 
lactic,  oxalic,  butyric,  in  combination  with  alkalin 
and  earthy  bases.  (2)  Organic  substances,  e.  g.,  alco- 
hol, glycerin,  cholesterin.  (3)  Pigments  found  in  the 
bile,  urine.  (4)  Nitrogenized  (crystalline),  as  urea, 
uric  acid,  xanthin,  creatin,  creatinin,  and  hippuric 
acid.     (Brubaker.) 

QUESTIONS 

1.  What  does  an  analysis  of  the  human  body  show  it  to  consist 
of?  To  what  groups  of  chemic  and  plant  world  do  these  compounds 
belong? 

2.  What  do  you  understand  by  the  term  proximate  principles? 

3.  What  do  the  organic  compounds  consist  of?     The  inorganic? 

4.  Name  the  chemical  elements  found  in  the  human  body. 

5.  What  chemic  compounds  found  in  the  human  body  represent 
the  carbohydrates? 

6.  What  do  the  carbohydrates  contain  and  in  what  proportion? 

7.  What  is  the  essential  benefit  derived  from  a  nourishment  rich 
in  carbohydrates? 

8.  Name  the  three  groups  of  carbohydrates? 

9.  Where  is  starch  found  in  the  vegetable  and  plant  world? 

10.  Where  is  dextrose  or  grape-sugar  found?  Levulose  or  fruit- 
sugar?    Saccharose  or  cane-sugar?    Lactose  or  milk-sugar? 

11.  Do  fats  belong  to  the  organic  or  inorganic  group  of  compounds? 

12.  Are  they  as  valuable  as  carbohydrates  as  a  source  of  heat 
and  energy? 


28      CHEMIC  COMPOSITION  OF  THE  HUMAN  BODY 

13.  Where  is  fat  usually  found  in  the  human  body?    In  the  animal 
foods? 

14.  Does  fat  contain  carbon,  hydrogen,  and  oxygen? 

15.  Name  the  three  neutral  intermixed  fats  which  are  found  in 
animals. 

16.  What  do  you  understand  by  saponification? 

17.  How  are  soaps  formed?     What  is  the  difference  between  a 
hard  and  soft  soap? 

18.  Where  are  proteins  found  in  the  vegetable  world?     Animal 
world? 

19.  What  do  proteins  contain? 

20.  Why  are  proteins  so  essential  to  the  tissues  of  the  body? 

21.  What  are  proteoses  and  peptones? 

22.  What  percentages  of  water  comprises  the  body  weight? 

23.  Name  the  inorganic  salts  found  by  analysis  in  the  body  tissues. 

24.  Where  is  phosphorus  found   in  the   body  tissues?     Sodium 
chlorid?    Sulphur?    Iron? 


CHAPTER  III 

METABOLISM  — THE  CELL,  ITS  STRUCTURE 
AND  FUNCTIONS 

METABOLISM 

Metabolism  is  the  term  used  to  express  the  various 
and  complex  phenomena  which  are  taking  place  within 
the  protoplasm  of  the  cells  of  the  tissues  throughout 
the  body,  whereby  the  food  principles  are  transferred 
into  simpler  or  complex  compounds  by  the  action  of 
digestion,  absorption,  etc.,  and  by  which  they  are 
carried  to  the  cells  of  the  tissues  where  they  are  again 
converted  into  other  bodies  by  an  inherent  function 
of  the  protoplasm  of  the  cells,  and'  produce  energy 
that  is  later  transferred  into  heat  and  activity. 

Oxygen  is  essential  to  this  chemic  change  going  on 
within  the  cells.    But  oxygen  is  not  a  food. 

When  food  is  broken  up  into  simple  compounds 
it  is  termed  katabolism;  and  when  transformed  into 
complex  chemic  bodies  it  is  called  anabolism.  Both 
of  the  above  changes  are  continually  going  on  within 
the  body  and  together  comprise  the  processes  of 
metabolism. 

The  body  to  develop,  grow,  and  perform  the  various 
functions  which  constitute  life,  requires  material  for 
the  tissues.  This  is  derived  from  the  food  we  eat  and 
liquids  we  drink;  and  the  oxygen  we  breathe  from  the 
air  is  essential  to  promote  metabolism.  The  food 
is  used  by  the  tissues  and  the  waste  materials  result- 
ing from  the  processes  of  metabolism  are  eliminated. 


30  METABOLISM 

Food,  then,  is  not  only  used  to  create  energy,  heat, 
and  activity,  but  it  must  replace  the  loss  of  tissue  in 
the  body  which  is  continually  occurring  during  the 
performance  of  the  processes  of  life,  from  birth  to  old 
age.  When  this  waste  is  not  replenished  by  new  tissue, 
the  body  cannot  properly  carry  on  its  functions. 

Every  effort  of  the  human  body  requires  a  certain 
amount  of  energy  or  force  to  bring  about  its  perform- 
ance. Thus  a  man  in  his  daily  work  lifts  a  certain 
weight;  the  body  cells  must  reproduce  and  furnish  a 
proportionate  amount  of  heat  and  activity  necessary 
to  accomplish  this  effort.  This  he  obtains  from  the 
energy  developed  from  a  definite  amount  of  food 
eaten  each  day. 

Food  is  held  together  by  a  force  called  potential 
energy.  When  broken  up  into  its  more  absorbable 
substances  by  the  process  of  digestion,  etc.,  so  that 
the  cells  of  the  tissues  can  make  use  of  it,  to  develop 
energy  it  is  said  to  have  kinetic  energy. 

It  is  essential  to  determine  the  heat  value  of  various 
foods,  in  other  words,  to  find  out  how  much  heat  and 
energy  will  be  derived  from  the  difi'erent  foods  after 
their  ingestion  and  digestion,  etc.  This  may  be  deter- 
mined experimentally  by  the  use  of  an  instrument 
known  as  a  bomb  calorimeter,  the  result  being  expressed 
in  calories.  A  calorie  is  the  amount  of  heat  that  is 
necessary  to  raise  the  temperature  of  1  kilogram  of 
water  1°  C.  (It  is  nearly  equal  to  the  amount  required 
to  raise  one  pound  of  water  4°  Fahrenheit.)  This 
expressed  in  mechanical  force,  means  that  a  calorie 
would  raise  a  ton  about  1.54  feet,  or  that  it  is  equal 
to  1.54  foot-tons. 

The  number  of  calories  required  to  furnish  heat  and 
energy  sufficient  to  accomplish  a  certain  amount  of 
activity  varies,  depending  upon  the  age,  sex,  amount 
of  work,  mental  and  physical,  and  climatic  conditions. 
It  is  essential  to  know  how  many  calories  are  required 
to  perform  a  certain  amount  of  work  from  the  taking 


THE  CELL 


31 


of  various  foods  into  the  body,  to  make  a  proper  appli- 
cation of  dietetics  in  the  feeding  of  healthy  and  diseased 
persons. 


Nuclear  iniemhrnne^ 


Fluid 
contents  of 
network 


Yotoplasmic 
framework 


.Microsome — — 

Nuclear  fluid 
fibrillar  substance 


Fig.  I 


Nuclear 
framework 

Nucleolus 


)  Archoplnsm 


l)  cent) 


■Fibrillar  substance 
Microsome 


Diagram  of  a  cell.  The  lower  segment  illustrates  the  fibrillar  theory,  the 
upper  the  granular  theory,  the  left  the  foam  theory.  At  the  right  the  proto- 
plasmic threads  radiate  from  the  centrosome.  The  nuclear  network  consists 
of  nuclein,  linin,  and  lantanin.      (Symonowicz.) 


THE   CELL 

The  cell,  protoplasm  or  bioplasm  is  the  anatomic 
and  physiologic  bases  of  the  body.  All  growth,  repair, 
disintegration,  heat,  energy,  and  life  of  the  tissues 
(whether  normal  or  abnormal)  depend  upon  the  histo- 
logic cell  as  a  unit  to  work  upon.     Cells  are  seen  only 


32  THE  CELL,  ITS  STRUCTURE  AND  FUNCTIONS 

microscopically.  They  vary  in  size  and  may  measure 
from  ^TTxr  o^  ^^  i^ch,  the  diameter  of  a  red  blood  cell, 
to  "5^^  of  an  inch — ^the  diameter  of  the  large  cells  in 
the  gray  matter  of  the  spinal  cord.  The  structure  of 
a  cell  consists  of  a  gelatinous  substance,  usually  homo- 
geneous, called  protoplasm  or  cytoplasm,  containing 
a  small  spheric  body,  the  nucleus,  which  latter  con- 
tains the  nucleolus.  Young  cells  appear  clean,  mature 
cells  contain,  depending  on  the  tissue  they  are  found 
in,  different  substances,  e.  g.,  fat-globules,  granules  of 
glycogen,  mucigen,  pigments,  and  digestive  ferments. 
Cells  possess  the  power  of  changing  their  shape,  and 
are  also  capable  of  growth,  nutrition,  and  reproduction. 

Growth. — Newly  reproduced  cells  are  very  small, 
but  they  soon  grow,  owing  to  their  characteristic 
organization  and  surrounding  medium,  to  resemble 
the  normal  adult  cell  of  a  given  tissue. 

Nutrition. — Cells  not  only  must  grow,  but  they  have 
to  repair  or  make  up  the  loss  from  waste,  etc.  Growth 
and  nutrition  are  dependent  not  only  upon  the  power 
possessed  by  living  material  of  absorbing  its  nutrition 
from  the  lymph,  but  also  upon  the  property  of  taking 
that  nutrition  and  converting  it  into  material  similar 
to  its  own,  before  waste  took  place,  and  then  endow- 
ing it  with  physiologic  functions.  Thus  we  have  a 
cell  doing  work,  wasting  as  a  result  of  such  labor; 
repairing  not  only  its  own  body,  but  renewing  its 
powers  of  doing  fresh  work. 

Reproduction. — Cells  reproduce  themselves  by  two 
methods,  direct  and  indirect  division.  (See  Figs.  2  to 
16,  pages  36  to  39.) 

Direct  division  is  seen  when  the  nucleus  of  cells 
becomes  narrowed  and  divides  with  a  grouping  of  the 
nuclear  elements.  This  is  believed  to  occur  only 
where  cell  disintegration  occurs.  Indirect  division — 
this  is  called  karyokinesis — is  a  complex  process  and 
its  main  feature  is  due  to  the  centrosome  of  a  cell 
becoming  enlarged    and  in  leaving  the  nucleus  lying 


THE  CELL  33 

in  the  surrounding  protoplasm.  The  chromatin 
becomes  contracted  and  is  seen  as  V-shaped  loops 
(chromosome),  with  thin  closed  ends  pointed  toward 
the  common  centre,  the  polar  field.  The  mother 
stars  are  formed,  which  rapidly  give  origin  to  daughter 
stars,  in  which  the  chromatin  can  be  seen  as  two 
separate  nuclei  grouped  in  a  single  mass  of  protoplasm; 
at  this  stage  the  protoplasm  becomes  constricted 
and  two  separate  cells  are  seen  lying  in  their  own 
protoplasm.     (See  Figs.  2  to  8,  pages  36  and  37.) 

Cells  of  the  animal  and  human  body,  or  in  fact  all 
living  protoplasms,  possess  the  properties  of  irritability, 
conductivity,  and  motility. 

Irritability  or  the  power  of  responding  to  some  exter- 
nal excitant.  This  can  be  mechanic,  chemic,  or  electric; 
thus  if  the  protoplasm  acted  upon  be  muscle,  it  will 
contract;  if  a  gland,  such  as  the  parotid,  saliva  will 
be  secreted;  if  a  nerve,  a  sensation,  as  when  we  apply 
heat,  cold,  etc.,  to  the  skin;  or  other  nerve  activity, 
as  seen  in  the  contraction  of  the  pupil  when  one  looks 
suddenly  at  a  bright  light.  It  must  be  remembered 
that  the  degree  of  the  response  in  the  foregoing  depends 
upon  the  protoplasm  acted  upon  and  the  nature  and 
strength  of  the  irritating  principle. 

Conductivity  is  developed  best  in  muscle  and  nerves, 
as  seen  when  molecular  disturbances  occur  at  the  ex- 
tremity of  the  peripheral  nerves,  and  are  conducted 
to  the  brain,  and  the  same  phenomena  arising  in  the 
brain  are  transmitted  to  the  peripheral  nerves. 

Motility  is  the  power  possessed  by  cells  of  apparent 
active  movement  in  response  to  natural  causes,  which 
scientists  have  not  yet  determined.  This  motility  is 
best  seen  by  microscopic  technique  and  observed  in  the 
ameboid  movements  of  the  white  cells  of  the  blood, 
the  waving  of  cilia,  the  activities  of  the  spermatozoons 
and  ova  during  impregnation,  or  the  commencement 
of  pregnancy,  etc. 


34     THE  CELL,  ITS  STRUCTURE  AND  FUNCTIONS 


QUESTIONS 

1.  Describe  the  term  metabolism. 

2.  Is  oxygen  considered  a  food? 

3.  What  do  you  understand  by  the  term  katabolism?  Anabo- 
lism? 

4.  Why  is  food  essential  to  the  body's  requirements? 

5.  What  is  meant  by  a  calorie? 

6.  What  term  is  used  that  expresses  the  determination  of  the 
amount  of  heat  and  energy  to  be  derived  from  the  different  foods 
we  eat  and  digest? 

7.  What  factors  will  vary  the  determination  of  the  number  of 
calories  required  to  furnish  a  certain  amount  of  heat  and  energy 
from  the  food  we  eat? 

8.  What  histologic  unit  underlies  all  the  phenomena  of  physio- 
logic life  as:  growth,  repair,  disintegration,  heat,  energy,  and  life 
of  the  tissues? 

9.  What  functions  is  a  cell  capable  of? 

10.  How  do  cells  derive  their  nutrition?    Repair  waste?    Renew  its 
functional  properties? 

11.  How  do  cells  reproduce  themselves? 

12.  Describe  the  term  karyokinesis. 

13.  Name  the  properties  of  a  cell. 

14.  What  externa]  stimulus  will  produce  irritability  in  a  cell? 

15.  What  do  you  understand  by  the  term  as  used  in  connection 
with  the  properties  of  a  cell-irritability?    Conductivity?    Motility? 


CHAPTER   IV 
TISSUES 

To  grasp  an  understanding  of  the  various  tissues 
properly,  a  brief  description  of  the  cells  from  which 
they  are  developed,  embryologically,  will  be  necessary. 

The  Ovum. — The  ovary  secretes  a  cell,  the  original 
cell  of  the  female  human  body,  called  the  ovum.  The 
ovum  consists  of  a  limiting  wall,  the  vitelline  membrane, 
enclosing  the  protoplasm,  vitellus,  which  consists  of 
two  parts — the  dentoplasm  or  nutritive  yolk,  and  the 
animal  protoplasm  or  formative  yolk.  Within  the 
vitellus  is  found  the  nucleus  or  germinal  vesicle,  which 
contains  the  nucleolus  or  germinal  spot. 

Before  an  ovum  can  develop  into  an  offspring  it 
must  undergo  numerous  complex  changes.  The  two 
most  important  phenomena  are  defined  as  maturation 
and  fertilization. 

Maturation. — Maturation  or  ripening  is  the  process 
taking  place  in  the  ovum,  which  prepares  it  for  the 
reception  of  the  male  element — spermatazoon,  where 
its  contained  chromatin  and  a  small  part  of  the  proto- 
plasm are  collected  into  the  form  of  two  minute 
structures  called  polar  bodies,  when  a  modified  cell 
reproduction  or  karyokinesis  occurs.  This  reproduc- 
tion must  take  place  before  ova  can  be  fertilized. 

Fertilization.^ — ^This  is  the  process  in  which  the  male 
and  female  units — the  ovum  and  spermatozoon — unite 
to  form  a  complete  and  perfect  cell,  by  division, 
which  ultimately  develops  into  cells  which  form  the 
tissues  of  the  whole  body. 

The  male  element  or  spermatozoon  or  spermium  con- 
sists of  a  head,  middle-piece,  and  tail.    After  entering 


36  TISSUES 

Fig.  2  Fi«    3 


FiQ.  4 


Fia.  5 


Fig.  6 


i^50  t:- 


'■■4^' 


Diagrams  illustrating  cell  division — karyokinesis. 


THE  OVUM  37 

Fig,  7  Fia.  8 


\ 


Semidiagrammatic  representation  of  the  processes  of  cell  and  nuclear  division 
(karyokinesis)  in  Ascaris  megalocephala.     (After  Kostanecki.) 

Fig.  2. — Resting  cell. 

Fig.  3. — Division  of  centrosome. 

Fig.  4. — Prophase — centrosomes  at  the  'poles;  radiation  well-developed; 
chromatin  net-work  broken  up  into  four  chromosomes. 

Fig.  5. — Mother-star  stage  (monaster);  chromosomes  arranged  at  the 
equator. 

Fig.  6. — Metaphase;  the  longitudinally  divided  chromatin  filaments  moving 
toward  the  poles. 

Fig.  7. — Anaphase;  beginning  of  division  of  cell  body. 

Fig.  8. — Division  of  cell  body  almost  completed;  the  central  spindle  shows 
the  beginning  of  the  intermediate  bodies. 


the  ovum  the  head  and  middle-piece,  representing 
the  nucleus  and  centrosome,  respectively,  of  a  cell 
from  the  testicle  (the  male  organ,  the  cells  of  which 
secrete  the  spermatozoon)  form  eight  chromosomes. 
The  chromatin  of  the  germinal  vesicle  of  the  ovum 
also  forms  eight  chromosomes.  The  process  continues 
within  the  cell  until  thirty-two  chromosomes  are  de- 
veloped by  longitudinal  cleavage;  these  are  subdivided 
into  sixteen  chromosomes,  which  enter  each  diaster  or 
daughter  cell. 


38 


TISSUES 


I  R  Sp 


Fig.  11 


Fig.  12 


//  R  Sp 


Stages  in  the  fertilization  of  Physa  fontinalis. 
Wierzejski.) 


(After  Kostanecki  and 


Fig.  9. — Mother-star  stage  passing  into  metakinesis  for  the  formation  of 
the  first  polar  body.    The  spermatozoon  is  enclosed  in  the  egg  in  toto. 

Fig.  10. — Formation  of  first  polar  body;  centrosome  divided. 

Fig.  11. — First  polar  body  formed.  Monaster  stage  for  the  formation  of 
the  second  polar  body.    Sperm  radiation  is  separated  from  the  sperm  nucleus. 

Fig.  12. — Formation  of  the  second  polar  body.  Sperm  radiation  with  two 
centrosomes  near  the  vesicular  sperm  nucleus. 


THE  OVUM 


39 


Fig.  43 


(^^^-^~')~-//  R  K 


FA  K 


Fig.   14 


/  R  K- 


II  R  K- 


FA  K 

\ 


^pK 


■^i> 


;^^  ^  St 


Fig.   16 


/  F  >7' 


-%^ 


Fig.  13. — Two  polar  bodies  above.  Egg  nucleus  has  become  vesicular. 
Sperm  radiation  has  increased  in  size. 

Fig.  14. — Egg  and  sperm  nuclei  approach  one  another.  The  sperm  radia- 
tion and  the  centrosomes  move  apart. 

Fig.  15. — Egg  and  sperm  nuclei  closely  approximated.  The  centrosomes 
arrange  themselves  on  opposite  sides. 

Fig.  16. — The  chromosomes  of  the  egg  and  sperm  nuclei  form  a  monaster 
stage  to  give  rise  to  two  new  cells. 

CSpK,  central  spindle;  EiK,  egg  nucleus;  IFSp,  first  spindle  after  fertiliza- 
tion; G,  tail  of  spermatozoon;  IRK,  first  polar  body;  II RK,  second  polar 
body;  IRSp,  first  polar  spindle;  IIRSp,  second  polar  spindle;  SpC,  centro- 
some  of  spermatozoon;  SpK,  sperm  nucleus;  SpSt,  sperm  radiation. 


40  TISSUES 

After  fertilization  the  ovum  divides  and  redivides 
into  numerous  cells,  forming  an  irregular  mass  termed 
the  mulberry  mass  or  morula.  The  latter  collection  of 
cells  divides  again  into  an  outer  and  inner  cell  mass 
called  the  blastula.  The  outer  mass  is  supposed  to  dis- 
appear, while  the  inner  continues  to  develop  and  forms 
two  layers — an  outer,  the  ectoderm  or  epiblast,  and  an 
inner,  the  entoderm  or  hypoblast.  This  is  termed  the 
gastrala  or  diploblast.  A  third  layer  is  developed  from 
the  two  former  layers,  each  setting  aside  a  few  cells 
which  develop  the  third  layer,  termed  the  mesoderm 
or  mesoblast,  that  lies  between  the  two  layers.  The 
formation  receives  the  name  of  blastodermic  •vesicle  or 
triploblast. 

All  tissues  of  the  body  are  composed  of  cells  arising 
from  the  cells  in  the  original  three  layers  of  the  triplo- 
blast or  blastodermic  vesicle.  Tissues,  which  are  always 
studied  microscopically,  consist  of  cells  held  together 
by  an  intercellular  cement,  and  perform  a  definite 
function;  thus  they  may  be  supportive,  as  bone,  etc., 
or  functional,  as  the  liver,  etc.  All  the  tissues  to  be 
seen  and  understood  in  their  minute  arrangement  are 
first  treated  by  histologic  methods  in  the  laboratory 
by  hardening,  sectioning,  fixing,  dehydrating,  staining, 
etc.,  and  are  then  observed  under  the  microscope. 
This  process  is  not  essential  to  the  nurse's  knowledge, 
but  should  she  desire  a  complete  understanding  of 
the  subject  she  should  refer  to  the  standard  works  on 
histology. 

Tissues  are  divided  into  epithelial,  comiective, 
muscle,  and  nerve 

Epithelial  Tissue  or  Epithelium. — They  may  be  pro- 
tective, as  the  cells  of  the  skin  and  conjunctiva  of  the 
eye;  secretive,  as  the  cells  of  the  pancreas,  parotid 
gland,  etc.;  excretive,  as  the  cells  of  the  kidneys; 
to  prevent  friction,  as  those  seen  in  the  cells  of  the 
synovial  sacs  between  the  articulating  cartilages  of 
joints,  peritoneum,  and  layers  of  pleura.     Epithelial 


SQUAMOUS  CELLS  41 

cells  line  cavities  that  normally  communicate  with 
the  air/  except  the  pleural,  peritoneal,  and  synovial 
sacs,  and  between  the  articulating  cartilages  of  joints. 
Epithelial  cells  are  classified  usually  as:  (1)  squa- 
mous, simple  and  stratified;  (2)  columnar,  simple,  modi- 
fied, and  stratified;  (3)  ciliated,  simple  and  stratified; 
(4)  prickle  cells;  (5)  goblet  cells;  (6)  transitional  cells; 
(7)  pigment;  (8)  neuro-epithelial;  (9)  glandular. 

Ftg    17 


Flat  epithelial  cells  isolated  from  the  oral  mucous  membrane  of  man.     X  375 
(Szymonowicz.) 


1.  Squamous  Cells. — (a)  Simple  squamous  cells  con- 
sist of  a  single  layer  of  flattened  elements,  each  con- 
taining a  nucleus,  usually  situated  in  the  centre  and 
oval  in  form.  They  are  found  in  the  alveoli  of  the 
lungs,  ventricle  of  brain,  descending  limb  of  Henle's 
loop  in  the  kidney,  and  Bowman's  capsule  of  kidney. 

(6)  The  stratified  squamous  cells  consist  of  layers 
of  cells  one  on  top  of  the  other.  The  lowest  layer, 
the  germinal  stratum,  is  arranged  in  columns,  those 
above  being  polygonal.  As  the  surface  is  reached 
the  cells  become  more  flattened,  forming  the  squames 
or  scales.  These  cells  are  usually  found  when  they 
afford  the  most    protection,  as  the  skin  (epidermis) 


42 


TISSUES 


lining  the  mouth  cavity,  pharynx,  esophagus,  epiglottis, 
vocal  cords,  and  the  anus  and  vagina. 


Fia.  18 


Diagram  of  flat  epithelium.  I,  seen  from  above;  II,  seen  from  the  side 
after  transverse  section  on  the  line  m.  (a)  cell  boundaries  as  straight  lines; 
(6)  cell  boundaries  as  wavy  lines.    (Szymonowicz.) 


.,.1 

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9Y9  Yeie  I  •T'/ »Ye  1  oToY 

Diagrams  of  epithelium:  o,  nuclei  at  various  levels;  b,  stratified  pave- 
ment epitheUum;  c,  stratified  cylindrical  epithelium,  ciliated  at  the  right. 
(Szymonowicz.) 


2.  Columnar  Cells. — (a)  Simple  columnar  cells  are 
arranged  in  tall  columns  consisting  of  a  single  layer  with 
a  nucleus  situated  at  the  base  of  each  cell.  They  are 
found  in  the  stomach  and  intestinal  tract,  anterior 
portion  of  the  male  urethra,  glands  of  Cowper  and 
Bartholin,  prostate,  gall-bladder,  seminal  vesicles,  and 
many  gland  ducts.  Low  columnar  cells  are  often 
called  cuboidal. 


GOBLET  CELLS  43 

(6)  Modified  or  pseudostratified  cells  are  simple 
columnar  or  ciliated  cells  in  which  the  nuclei  are  at 
different  levels,  thus  giving  the  appearance  of  several 
layers  of  cells.  These  cells  are  found  as  ciliated 
elements  in  the  oviduct,  uterus,  and  middle  ear,  and 
as  non-ciliated  elements  in  the  seminal  vesicles  and 
prostate. 

(c)  Stratified  columnar  cells  consist  of  numerous 
layers  of  cells  arranged  one  upon  another.  They  are 
found  in  the  lining  membrane  of  the  vas  deferens 
(male),  membranous  urethra,  and  ducts  of  some  glands. 

3.  Ciliated  Cells. — (a)  Simple  ciliated  cells  are  ar- 
ranged in  a  single  layer  of  columnar  cells  which  have 
upon  their  exposed  surface  fine  cilia  or  hair-like  pro- 
cesses; they  possess  motion  that  is  always  directed 
toward  the  outlet  of  the  organ  in  which  they  are 
located.  They  are  found  in  the  smaller  bronchioles, 
spinal  canal,  accessory  spaces  of  the  nasal  cavities, 
and  the  ventricles  of  the  brain. 

(6)  Stratified  ciliated  cells  are  the  same  as  the 
stratified  columnar,  with  the  cilia  attached  only  to 
the  cells  of  the  exposed  layer.  These  cells  are  found 
in  the  epididymis  (male),  first  portion  of  the  vas 
deferens  (male).  Eustachian  tube, 
upper  part  of  the  pharynx,  larynx,  ^^Q-  20 

trachea,  and  nasal  tract. 

4.  Prickle  Cells. — These  are 
polygonal  elements  that  possess 
little  spines,  which  project  from 
the  sides  of  the  cells,  and  pass 
to  meet  spines  of  other  cells,  thus 
preventing  the  cells  from  meeting, 
at  the  same  time  forming  inter-  prickie  ceiis.  (Gerrish.) 
cellular  bridges  or  spaces.     They 

are  found  in  the  epidermis  (skin)  just  above  the  genetic 
layer. 

5.  Goblet  Cells. — These  are  cells  resembling  the 
cylindric    type,    distended    with    a    secretion    called 


44 


TISSUES 


mucin.  On  filling  they  resemble  a  goblet.  When 
the  secretion  has  been  discharged  these  cells  become 
long  and  slender,  the  part  containing  the  nucleus 
extending  on  either  side.  They  are  found  in  the 
gastro-intestinal  and  respiratory  tracts. 


ail 


Cell  body 


Nucleus — 


FiQ.  21 

Impression  made  by 
neighboring  cell  Mucus 


—  Oxflet 


Cell  membrane 


i- — Protoplasm 
'iijL. — yuclens 


Two  ciliated  cells  and  two  goblet  cells  isolated  from  the  frog's  esophagus. 
X  520. 


6.  Transitional  Cells. — These  are  stratified  cells  be- 
longing to  neither  the  squamous  or  columnar  groups. 
They  are  polygonal;  found  in  the  pelvis  of  the  ureter, 
in  the  ureter,  bladder,  the  first  part  of  the  male  and 
almost  the  entire  length  of  the  female  urethra. 

7.  Pigmented  Cells. — These  are  polygonal  or  colum- 
nar in  shape,  the  protoplasm  containing  pigment. 
They  are  found  in  the  epidermis  of  the  colored  races, 
and  around  the  nipple  and  genitals  of  the  Caucasians, 
as  polygonal  cells,  and  in  the  retina  of  the  eye  where 
they  assume  the  columnar  shape. 

8.  Neuro-epithelial  Cells. — These  are  cells  which  have 
become  so  differentiated  as  to  perform  a  special  sense 
function.    These  are  found  in  the  retina  of  the  eye,  in 


GLANDS  45 

the  internal  ear  (hair  cells),  in  the  olfactory  mucous 
membran^,  in  the  taste-buds  of  the  tongue,  and  tactile 
cells  in  the  epidermis. 

9.  Glandular  Cells. — These  are  found  in  the  pancreas, 
liver,  etc.,  and  their  shape  varies  according  to  the 
gland  in  which  they  are  found. 

Mucous  Membranes. — All  the  surfaces  of  the  gastro- 
intestinal and  pulmonary  tracts,  genito-urinary  appar- 
atus, etc.,  within  the  body  are  covered  by  epithelial 
cells,  called  mucous  membranes,  These  membranes 
are  protected  in  the  various  organs  by  a  superficial 
layer  of  cells — their  variety  depending  on  the  tissue 
they  are  found  in — which  we  have  described  above. 
Beneath  this  layer  the  cells  rest  upon  a  delicate  base- 
ment membrane,  the  next  layer  is  the  tunica  propria 
consisting  of  a  layer  of  fibro-elastic  tissue.  Within 
this  layer  are  lodged  the  capillary  bloodvessels, 
nerves,  lymphatic  spaces  or  channels,  and,  in  certain 
organs,  glands  and  lymphoid  tissue.  These  thin  layers, 
are  seen  resting  on  a  fourth  peripheral  layer,  called 
the  muscularis  mucosae,  consisting  of  involuntary 
(not  under  the  control  of  the  will),  non-striated  muscle 
tissue.  This  layer  is  sometimes  wanting  in  some  tissues. 
The  above  mucous  membranes  line  cavities  which 
communicate  with  the  air.  Their  cells  usually  secrete 
a  substance  called  mucin. 

Glands. — Glands  are  considered  under  the  classifica- 
tion of  epithelial  tissues.  They  are  simply  various 
shaped  pouches  or  tubes  of  mucous  membranes  grow- 
ing out  from  the  superficial  surface  of  the  tissue  in 
which  they  are  located.  All  glands  are  lined  with 
epithelial  cells  arranged  in  different  groups,  and 
possessing  a  physiologic  function.  These  groups  of 
cells  are  the  units  from  which  the  organs  develop 
their  secretions. 

Glands  are  subdivided  into  (1)  tubular,  simple, 
branched,  coiled,  compound;  (2)  tubulo-alveolar ;  (3) 
alveolar,  or  racemose  glands,  simple  and  compound. 


46 


TISSUES 


These  different  shaped  glands  are  lined  by  epithelial 
cells,  depending  on  the  situation  and  function.  Their 
secretions  are  liquid,  and  may  be  serous,  mucous,  or 
mixed,  which  the  lining  cells  secrete  as  needed  by  the 
organ  to  perform  its  physiologic  function. 


Fig.  22 


Tubular  glaads. 


Alveolar  glands. 


^J^ 


m'dm 


Diagram  of  various  forms  of  glands;   a,  duct;  x,  simple  tubule;   xx,  simple 
alveolus.     (After  Szymonowicz.) 


Serous  Membranes. — They  are  membranes  covered 
by  a  single  layer  of  flattened  cells,  with  a  large  pro- 
jecting nucleus;  these  cells  are  held  together  by  a 
intercellular  cement.  They  are  termed  endothelial 
cells.  Serous  membranes  never  have  a  basement 
membrane  and  line  cavities  that  do  not  communicate 
with    the    air.      These    membranes    appear    smooth, 


CONNECTIVE  TISSUES 


47 


glisteniag,  and  transparent.  Openings  called  stomata 
are  said  to  be  present  between  the  cells,  but  they  are 
supposed  to  be  artefacts  according  to  the  latest  teach- 
ing. Serous  membranes  line  joint-cavities,  bursse, 
tendon  sheaths,  circulatory  and  lymphatic  systems, 
and  the  pleural,  pericardial,  and  peritoneal  cavities. 


Fig.  23 


Fia.  24 


White  fibrous  tissue.     (Gerrish.) 


Yellow  fibrous  tissue. 
(Queckett.) 


Connective  Tissues. — The  connective  tissues  of  the 
body  are  the  elements  entering  into  the  formation 
of  the  more  permanent  structures  of  the  body,  such 
as  bones,  cartilages,  ligaments,  those  holding  fat  in 
position,  those  used  as'  coverings  for  muscles — as 
fascia,  as  sheaths  for  bloodvessels,  and  nerves,  as 
supports  for  cells  of  glands  and  organs,  and  those 
binding  membranes  to  underlying  organs,  as  the 
pleura  and  peritoneum  to  the  lungs  and  abdominal 


48  TISSUES 

organs  respectively.   The  connective  tissues  are  derived 
from  the  mesoderm. 

They  are  classified  as  follows:  (1)  fibrous;  (a)  loose, 
(h)  dense;  (2)  yellow  elastic;  (3)  mucous;  (4)  retiform; 
(5)  mixed  or  areolar;  (6)  adipose  or  fatty;  (7) 
l3rmphoid;  (8)  cartilage;  (9)  bone;  (10)  dentin  (teeth); 
(11)  blood. 

1.  Fibrous  Tissue. — (a)  The  loose  variety  consists  of 
fine  thread-like  fibers  held  in  bundles  by  a  small 
quantity  of  cement  substance,  and  scattered  through- 
out those  groups  of  fibrils  are  seen  a  few  cells.  This 
variety  is  mostly  for  the  support  of  capillary  blood- 
vessels, the  capsules  of  organs,  and  as  a  suppurative 
element  in  the  tunica  propria  and  submucosa  in  the 
mucous  membrane  of  the  respiratory  and  alimentary 
tracts. 

(6)  The  dense  variety  differs  from  the  former  in 
the  fibrils  being  thicker  and  the  bundles  larger.  The 
dense  is  best  seen  in  tendons  of  muscles,  when  it  occurs 
as  parallel  bundles.  Seen  under  the  microscope  on 
a  cross-section  the  whole  structure  is  seen  surrounded 
by  a  loose  sheath  of  fibers,  the  epitendineum,  from  which 
septa  are  seen  passing  into  and  dividing  it  into  dis- 
tinct or  separate  bundles  of  fibers,  the  peritendineum. 
The  tendon  cells  are  seen  arranged  in  rows  lying 
between  the  individual  bundles  of  fibers. 

White  fibrous  tissue  is  very  strong,  inelastic,  is 
pearly  white  in  color,  as  seen  when  the  skin  is  removed 
and  dissections  made  of  ligaments  and  tendons.  It 
serves  as  a  stocking-like  covering  to  muscles,  where 
it  is  termed  fascia;  and  is  seen  as  a  bluish-white  mem- 
brane reinforcing  muscles  and  strengthening  their 
insertions  to  bones,  particularly  in  the  region  of  joints, 
called  an  aponeurosis. 

2.  Yellow  Elastic  Tissue.^ — This,  as  the  name  implies, 
possesses  elasticity;  the  fibrils  are  coarser  than  the 
white  variety.  It  is  found  in  the  ligamentum  nuchse, 
which  extends  from  the  occipital  bone  to  the  spinous 


CONNECTIVE  TISSUES 


49 


processes  of  the  cervical  vertebra,  along  the  vertebral 
column,  where  it  is  reinforced  by  white  fibrous  tissue, 
also  in  the  ligamentum  subflava,  in  the  vertebral 
column,  in  bloodvessels,  and  in  the  skin. 

3.  Mucous  or  Embryonic  Tissue. — This  is  found  in 
the  umbilical  cord  of  the  fetus.  It  is  at  first  homo- 
geneous, then  later  fibers  both  white  and  elastic  develop, 
the  former  in  bundles,  the  latter  generally  single. 
Among  these  fibers  are  a  few  scattered,  mostly  spindle- 
shaped,  some  stellate,  and  some  round  cells. 


Fig.  25 


Areolar  tissue,  composed  of  bundles  of  white  fibrous  tissue  and  branched 
strands  of  yellow  fibrous  tissue  loosely  intertwined.     (Gerrish.) 


4.  Retiform  or  Reticulum    Tissue. — This   forms   the 
frame-work  of    glands  and   gland-like   organs.     The 
fibrils  are  arranged  in  delicate  bundles,  in  the  meshes 
4 


50  TISSUES 

of  which  are  the  functionating  cells  of  the  glands. 
The  cells  of  this  variety  are  mostly  stellate. 

5.  The  Mixed  or  Areolar  Tissue.  —  This  contains 
both  white  and  elastic  tissue.  It  shows  a  net-work 
of  fine  white  fibrils,  with  elastic  fibrils  scattered 
throughout,  and  they  are  usually  branched.  The 
cellular  elements  scattered  among  these  fibrils  are 
stellate,  plasma,  and  wandering  forms.  Areolar  tissue 
is  very  fine,  delicate,  loose  in  texture,  and  binds  the 
skin  to  the  underlying  fasciae,  and  lies  between  muscles. 

6.  Adipose  or  Fatty  Tissue. — This  is  white  fibrous 
tissue,  in  which  fat  cells  are  deposited.  In  the  living 
body  it  is  liquid  at  the  temperature  of  the  body.  It 
can  only  be  seen  in  the  tissues  under  the  microscope 
after  special  preparation.  It  is  essential  to  know,  how- 
ever, that  it  is  found  and  can  be  seen  as  a  yellowish 
layer  beneath  the  skin  (postmortem),  surrounding 
organs,  etc.,  which  act  as  a  covering  or  protection  to 
them;  it  has  a  wide  distribution  and  is  never  found  in 
the  ear,  eyelid,  or  genitalia  (male),  and  is  always  found 
back  of  the  eye-ball  and  in  the  kidney,  no  matter  how 
poorly  nourished  an  individual  may  be,  even  to  the 
extent  of  starvation. 

7.  Lymphoid  Tissue. — This  is  made  up  of  a  net-work 
of  reticulum,  holding  among  its  fibers  the  white  blood- 
cells  or  leukocytes.  The  cells  seen  are  mostly  small 
lymphocytes,  and  some  large  lymphocytes  and  poly- 
nuclear  cells.  (See  blood,  page  221.)  There  are  three 
varieties  of  lymphoid  tissue:  (a)  diffuse;  (6)  solitary 
follicles;  (c)  Peyer's  patches;  and  lymph  nodes. 

(a)  The  diffuse  variety  is  found  in  the  tunica  propria 
of  the  mucous  membrane  of  the  alimentary  and  respir- 
atory tracts,  the  medulla  of  the  thymus  body,  and 
the  greater  portion  of  the  tonsil  and  spleen.  (6) 
Solitary  follicles  are  found  in  the  alimentary  and 
respiratory  tracts,  spleen,  and  tonsils.  (c)  Peyer's 
patches  consist  of  a  collection  of  solitary  follicles  clearly 
outlined  from  the  surrounding  tissue.    They  are  found 


CONNECTIVE  TISSUES  51 

in  the  wall  of  the  ileum  (the  terminal  portion  of  small 
intestines  which  opens  into  the  cecum).  Lymph  nodes 
(glands).     (See  Lymphatic  System.) 

8.  Cartilage. — Cartilage  is  not  as  compact  or  strong 
as  bone.  It  is  more  yielding;  thus  it  will  be  found  in 
different  parts  of  the  body  when  this  firm  yet  pliable 
property  is  essential  to  the  function  of  an  organ.  We 
see  it  in  the  cartilages  of  the  larynx,  where  one  may 
readily  understand  how  its  structure  must  be  more  or 
less  elastic  owing  to  the  constant  action  of  the  muscles 
upon  the  cartilages  and  their  change  in  relationship 
during  talking,  singing,  etc.,  and  its  value  can  be 
appreciated  when  placed  between  bones,  as  a  shock 
absorber;  demonstrated  by  the  intervertebral  disks 
between  each  vertebra. 

In  studying  the  structures  of  cartilage  it  is  con- 
sidered under  perichondrium,  cells,  and  intercellular 
substance.  The  perichondrium  is  a  fibrous  sheath 
which  surrounds  cartilage  and  corresponds  to  the 
periosteum  of  bone.  It  is  divided  into  an  outer  fibrous 
layer  containing  few  cells,  and  an  inner  portion  or 
chondrogenetic  layer,  consisting  of  flattened  and  elon- 
gated or  spindle-shaped  cells.  These  are  the  chondro- 
blasts  or  cartilage  cells.  The  latter  cells  are  seen  just 
beneath  the  perichondrium,  where  they  appear  as  flat 
cells,  then  as  the  centre  of  the  cartilage  is  reached 
they  become  more  oval  or  even  round.  Each  cell  is 
rich  in  protoplasm  and  contains  one  or  more  vacuoles. 
The  cell  is  surrounded  by  a  capsule,  and  a  small  space 
intervenes,  between  the  cell  and  the  capsule  called 
a  lacuna.  The  intercellular  substance  consists  of  a 
homogeneous  mass  in  the  hyaline  cartilage,  and  of 
white  fibrous  and  yellow  elastic  fibers,  in  the  white 
fibrocartilage  and  yellow  fibrocartilage  respectively. 

There  are  three  varieties  of  cartilage:  Hyaline, 
white  fibrocartilage,  and  yellow  fibro  or  elastic. 

The  hyaline  cartilage  is  pearl  blue  in  color,  is  elastic, 
and  cuts  with  a  knife.    It  is  found  in  the  body  covering 


52  TISSUES 

articular  surfaces  of  bones,  which  line  joint-cavities; 
in  costal  cartilages  as  found  between  the  ribs  and 
breast  bone  or  sternum;  in  cartilages  surrounding  the 
trachea  (windpipe);  and  in  most  of  the  laryngeal 
cartilages.     It  may  ossify  in  old  age. 

The  white  fibrocartilage  is  not  very  plentiful  and  acts 
as  a  structure  to  deepen  joint-cavities,  as  interarticular 
fibrocartilages  and  intervertebral  disks. 

Yellow  fibrocartilage  is  found  wherever  elasticity  is 
required,  as  in  the  epiglottis.  Eustachian  tube,  ear,  and 
smaller  laryngeal  cartilages.     It  never  ossifies. 

Cartilages  are  very  poorly  nourished,  as  they  do  not 
contain  many  bloodvessels,  except  in  the  perichon- 
drium; and  except  when  the  cartilage  is  developing. 
No  lymph  channels  are  present. 

Note. — ^Muscle,  osseous,  and  nerve  tissues  are  de- 
scribed under  the  chapters  on  Muscles,  Bones,  and 
Nerves  respectively. 


QUESTIONS 

1.  What  do  you  understand  by  the  term  maturation?    Fertiliza- 
tion? 

2.  What  three  layers  of  cells  are  developed  from  the  ovum  after 
maturation  and  fertilization  are  completed? 

3.  What  are  the  tissues  of  the  body  divided  into? 

4.  Name  the  functions  of  epithelial  tissue. 

5.  In  what  cavities  of  the  body  are  epithelial  cells  found? 

6.  Give  the  classification  of  epithelial  cells. 

7.  How  do  ciliated  cells  differ  from  other  cells? 

8.  What  is  characteristic  of  stratified  cells? 

9.  In  which  direction  do  the  motion  possessed  by  ciliated  cells 
point? 

10.  What  layers  of  tissues  enter  into  the  formation  of  a  normal 
mucous  membrane? 

11.  Which  layer  contains  bloodvessels,  lymphatic  spaces,  nerves, 
glands,  and  lymphoid  tissue  in  certain  organs? 

12.  Which  layer  contains  involuntary  non-striated  muscle  tissue? 

13.  Give  the  subdivisions  of  glands. 

14.  What  are  the  three  varieties  of  secretions  from  glands? 

15.  How  do  serous  membranes  differ  from  mucous  membranes? 

16.  What  name  is  given  to  the  type  of  cells  covering  the  serous 
membranes? 

17.  Where  are  serous  membranes  found  throughout  the  body? 


QUESTIONS  53 

18.  What  is  the  function  of  connective  tissue? 

19.  Give  the  classification  of  connective  tissues? 

20.  Where  is  yellow  elastic  tissue  found? 

21.  What  tissue  enters  into  the  frame-work  of  glands  and  gland- 
like organs? 

22.  Is  adipose  tissue  liquid  at  the  temperature  of  the  body? 

23.  What  structures  of  the  body  are  always  free  from  fat? 

24.  Name  the  three  varieties  of  lymphoid  tissue. 

25.  Is  cartilage  as  strong  as  bone? 

26.  What  is  the  essential  property  of  cartilage  as  found  in  the 
body? 

27.  Name  the  varieties  of  cartilage? 

28.  Describe  hyaline  cartilage  and  where  is  it  found?     Does  it 
ossify? 

29.  Where  do  you  find  white  fibrocartilage?    Yellow  fibrocartilage? 

30.  What  is  the  function  of  mixed  or  areolar  tissue? 


CHAPTER  V 

OSTEOLOGY— THE  DESCRIPTION  OF  BONES 
AND  BONE  TISSUE 

The  bones  entering  into  the  supportive  structure 
of  the  body  are  held  in  close  relation  with  each  other 
by  means  of  ligaments  and  muscles.  Thus  the  skeleton 
consists  of  a  strong,  firm  frame-work,  possessing  all 
manner  of  movements  due  to  the  action  of  the  attached 
muscles  and  the  leverage  of  the  bones,  allowed  by  the 
ligaments  holding  the  bones  in  relation  with  one 
another.  The  body  skeleton  consists  of  two  hundred 
and  six  bones,  as  follows: 

{Vertebral  column 26 
Skull 22 
Hyoid  bone 1 
Ribs  and  sternum 25 

—74 

AppendicularfUpper  limb 64 

skeleton     \Lower  limb 62 

—126 

Auditory  ossicles  (bones  of  ear) 6 

Total 206 

The  patellae,  two  in  number,  are  included  in  this 
list,  but  not  the  sesamoid  bones.  The  latter  are  small 
bones  (shaped  like  sesame  seed)  found  embedded  in 
tendons  covering  the  knee,  hand,  and  foot. 

Classes  of  Bones. — Bones  are  divisible  into  four 
classes:    long,  short,  flat,  and  irregular. 

Long  Bones. — These  are  found  in  the  limbs,  they 
support  the  weight  of  the  trunk  and  form  a  system  of 


CLASSES  OF  BONES  55 

levers  which  permit  the  power  of  locomotion  and 
prehension.  Long  bones  possess  a  shaft  and  an  upper 
and  lower  extremity.  The  shaft  or  the  diaphysis  is 
cylindrical,  containing  in  the  centre  a  hollow  cavity, 
the  medullary  canal,  in  which  during  life  is  the  bone- 
marrow.  Surrounding  this  is  dense  compact  tissue  of 
considerable  thickness,  but  not  so  thick  near  the 
extremities.  The  extremities  or  epiphyses  are  usually 
expanded  to  enable  one  bone  to  articulate  with  another 
and  to  afford  attachment  of  muscles.  They  are  usually 
developed  from  separate  centres  of  ossification  called 
epiphyses.  Examples  of  long  bones  are  the  femur  or 
thigh  bone,  the  humerus  or  bone  of  the  arm,  the  clavicle 
or  collar  bone,  the  radius  and  ulna  (bones  of  the  fore- 
arm), the  tibia  and  fibula  (bones  of  the  leg),  the  meta- 
carpal, metatarsal,  and  phalanges  (the  small  bones  of 
the  hand  and  foot)  respectively. 

Short  Bones. — These  are  found  in  that  portion  of  the 
body  where  strength  and  compactness  are  required 
and  the  motion  of  the  part  is  limited,  as  the  bones  of 
the  carpus  (wrist)  and  tarsus  (instep).  These  bones 
consist  of  cancellous  tissue  covered  by  compact  bone. 
They  are  held  firmly  together  by  ligaments.  Some 
include  the  patellae  and  sesamoid  bones  under  this 
variety. 

Flat  Bones. — ^These  are  found  wherever  protection 
is  required,  or  a  broad  surface  for  the  attachment 
of  muscles  is  essential,  as  the  bones  of  the  skull  and 
the  scapulae  (shoulder-blade) .  Flat  bones  are  composed 
of  two  thin  layers  of  compact  tissue,  between  which  is 
a  variable  amount  of  cancellous  tissue.  In  the  bones 
of  the  skull  these  layers  of  compact  tissue  are  termed 
the  tables  of  the  skull ;  the  innermost  is  thin  and  called 
the  vitreous  table.  The  cancellous  tissue  between  the 
layers  is  called  the  diploe. 

The  flat  bones  are  the  occipital,  parietal,  frontal,  nasal, 
lacrymal,  vomer,  scapula,  sternum,  ribs,  and  some  authors 
include  the  patella. 


56  OSTEOLOGY 

Irregular  Bones. — These  are  of  varying  shapes  which 
cannot  be  classified  under  any  of  the  preceding  groups. 
They  consist  of  a  layer  of  compact  tissue  externally 
enclosing  cancellous  tissue. 

The  irregular  bones  are :  the  vertebr8e,  sacrum,  cocc3rx, 
temporal,  sphenoid,  ethmoid,  malar,  maxilla,  mandible, 
palate,  turbinates,  and  hyoid. 

Surfaces  of  Bones. — The  examination  of  a  bone 
will  show  numerous  depressions  and  elevations  upon 
its  surface,  which  for  purposes  of  study  have  been 
classified  into  the  following  eminences  and  depressions: 
(1)  articular;  (2)  non-articular.     Examples  as  follows: 

Articular. — 

Eminences  (g^^^°J(f°^^^' 

[Head  of  humerus. 


Depressions(?^^^°i:^,«^^^*^ 
[Acetabulum  of 


Glenoid  cavity  of  scapula. 

OS  innominatum. 


Non-articular. — 


Eminences 


Depressions 


Tuberosity  is  a  broad,  rough,  uneven  elevation. 
Tubercle  is  a  small,  rough  prominence. 
Spine  is  a  sharp,  slender,  pointed  eminence. 
A  ridge,  line,  or  crest  are  narrow,  rough  elevations 
along  the  surface. 

Notches. 

Fossae. 

Grooves. 

Furrows. 

Fissures. 

All  are  of  variable  form. 


The  articular  eminences  and  depressions  are  the 
extremities  and  cavities  of  bones  which  enter  into  the 
formation  of  joints  respectively.  The  non-articular 
eminences  are  to  increase  the  surface  of  the  bone  for 
the  attachment  of  muscles  and  ligaments;  the  depres- 
sions usually  receive,  hold,  or  keep  in  position  tendons 
or  muscles,  and  transmit  bloodvessels  and  nerves. 


COMPOSITION  AND  STRUCTURE  OF  BONE     57 

Composition  and  Structure  of  Bone. — Bone  in  the 
fresh  state  is  pale  pink  in  color,  when  dried  it  is  grayish 
white.  The  constituents  of  dried  bone  are  31  per  cent, 
organic  matter  and  69  per  cent,  inorganic  matter. 
The  former  is  represented  by  bloodvessels  and  con- 
nective tissue,  and  proteins,  such  as  collagen,  ossein, 
elastin;  the  latter  by  mineral  salts,  e.  g.,  tricalcium  and 
magnesium  phosphate,  calcium  carbonate,  and  some 
soluble  salts.  These  ingredients  may  vary  with  the 
age  of  the  individual.  Thus  in  the  child  there  is  an 
increase  in  the  organic  matter  over  the  mineral  con- 
stituents, while  the  mineral  salts  predominate  in  bones 
of  the  adult.  This  absence  of  salts  in  the  bones  of 
children  accounts  for  the  elasticity  of  the  bones, 
and  when  fractured  they  bend  rather  than  break 
after  an  injury.  This  can  be  seen  when  a  fractured 
limb,  exposed  to  the  .T-rays,  will  appear  as  a  twig  bent, 
but  no  distinct  break  is  seen  (this  is  termed  a  green- 
stick  fracture).  On  the  other  hand  in  extremely  old 
persons  there  is  a  tendency  to  fracture  of  the  bones, 
due  to  the  increase  of  mineral  salts  over  the  organic 
constituents,  rendering  them  brittle,  and  unable  to 
withstand  the  slightest  strain  without  fracture.  Rick- 
ets is  another  example  of  this  decrease  in  lime  salts 
in  the  bones.  It  is  a  disease  occurring  in  children 
mostly,  characterized  by  a  bending  of  the  long  bones, 
and  deformity  of  the  limbs,  as  a  result  of  insufficient 
and  improper  nourishment.  Bone  belongs  to  the 
connective-tissue  group,  and  is  derived  from  the 
mesoderm  layer  of  the  tripoblast,  the  primitive  vesicle 
of  the  embryo. 

Periosteum. — All  bones  are  surrounded  by  a  fibrous 
sheath,  called  the  periosteum,  enclosing  the  bone  sub- 
stance; the  latter  is  composed  of  cells  and  intercellular 
substance.  The  periosteum  consists  of  two  layers: 
an  outer  fibrous,  supporting  bloodvessels,  an  inner 
or  genetic  layer,  rich  in  cells  and  blood  capillaries. 
The  cells  in  the  latter  become  the  future  osteoblasts 


58  OSTEOLOGY 

that  develop  the  osseous  tissue  by  a  process  of  cell 
secretion.  The  genetic  layer  gives  off  bundles  of  fibers 
which  pierce  the  layers  of  bone  at  right  angles  and 
bind  them  together.    These  are  called  Sharpey's  fibers. 

Bone  is  classified  as  to  its  composition  into  cancellous 
or  spongy,  compact  or  solid. 

Cancellous  or  Spongy  Bone. — This  consists  of  spicules 
forming  a  net-work  similar  to  a  sponge.  These  spicules 
have  a  fibular  structure,  and  between  them  are  small 
spaces  called  lacuna?  (little  lakes),  which  are  filled 
in  the  living  state  with  osteoblasts.  The  cancellous 
bone  is  found  in  the  head  of  long  bones,  the  centre 
of  flat  bones,  and  around  the  medullary  cavity.  In 
the  centre  of  all  long  bones  is  a  hollow  cavity  called 
the  medulla;  it  contains  marrow.  This  medullary 
cavity  is  lined  with  a  fibrous  layer  of  tissue  called  the 
endosteum,  which  covers  the  net-work  of  spongy  bone 
surrounding  the  medullary  canal. 

Compact  or  Solid  Bone. — This  is  the  stronger  of  the 
two  varieties  and  forms  the  outer  surface  of  the 
long  bones.  It  is  arranged  in  layers  called  lamellae, 
and  can  only  be  studied  in  section  after  preparation; 
and  when  observed  under  the  microscope  it  will  present 
a  series  of  lamellae  arranged  around  a  central  opening, 
called  the  Haversian  canal.  These  carry  bloodvessels 
in  a  longitudinal  direction  throughout  the  bone, 
and  communicate  with  each  other.  Between  the 
Haversian  canals  are  lacunae — lined  with  osteoblasts — 
they  communicate  with  each  other  and  the  Haversian 
canals  by  means  of  small  canals — called  canaliculi. 
Just  beneath  the  periosteum  the  lamellae  of  bone  are 
derived  from  it.  These  layers  have  between  them 
lacunae  with  canaliculi  connecting  each  other.  The 
most  external  lamellae  present  depressions  termed 
Howship's  foveae  or  lacunae;  these  are  filled  with  large 
bone-destroying  cells  called  osteoclasts.  Haversian 
canals  are  absent  in  the  external  lamellae  beneath  the 
periosteum,  but  large  canals  are  present,  containing 
blood  from  the  periosteum — Volkmann's  canals. 


BONES  OF  THE  HEAD  59 

The  H'kversian  canals  are  occupied  by  bloodvessels, 
nerves,  and  lymphatics,  except  in  the  region  of  the 
heads  of  long  bones;  owing  to  their  absence  this  por- 
tion of  the  bone  is  better  enabled  to  withstand  the 
pressure  imposed  upon  it.  The  above  arrangement 
of  canals  is  termed  the  Haversian  System. 

The  medullary  cavity  is  a  large  space  within  the 
centre  of  the  long  bones.  It  is  lined  by  a  fibrous  layer, 
the  endosteum,  and  contains  the  nutrient  marrow. 

Marrow  is  of  two  varieties,  red  and  yellow.  The 
former  color  is  seen  in  healthy,  young  individuals,  the 
latter  occurs  in  those  beyond  the  prime  of  life.  The 
presence  of  a  great  amount  of  fat  causes  the  latter  to 
assume  its  yellow  color.  The  cellular  elements  are  few 
or  are  wanting.  In  disease  it  may  become  red.  It  is 
derived  from  the  endosteum  between  the  compact  bone 
and  the  medullary  cavity,  and  consists  of  a  delicate 
frame-work  of  reticulum  holding  a  compact  capillary 
plexus  and  cells.  These  cells  are  classified  as:  Marrow 
cells  or  myelocytes,  nucleated  red  blood  cells  or  erythro- 
blasts,  white  blood  cells  or  leukocytes,  myeloplaxes.  (For 
a  better  knowledge  of  these  cells  the  reader  is  referred 
to  the  standard  works  on  histology  or  hematology.) 

The  function  of  red  marrow  is  to  produce  erythro- 
cytes, granular  leukocytes,  and  to  store  fat.  Bones 
are  nourished  by  an  artery  which  enters  the  nutrient 
foramen,  seen  on  the  surface  of  bones,  and  by  branch- 
ing into  smaller  vessels,  called  capillaries,  pass  into 
the  Haversian  canals  pother  vessels  enter  Volkmann's 
canals  to  nourish  the  most  external  lamellae  beneath 
the  periosteum. 


BONES    OF   THE    HEAD 

The  skull  is  divided  into  two  parts:  the  cranium 
and  face;  the  former  lodges  and  protects  the  brain 
and    its    membranes,   bloodvessels,   and    nerves;    the 


60  OSTEOLOGY 

bones  of  the  face  partially  surround  the  orbital  cavity 
and  form  the  walls  of  the  nasal  and  oral  cavities. 
The  cranium  has  eight  bones. 


(a)  Unpaired: 

Occipital. 
Sphenoid. 
Ethmoid. 

ib)  Paired: 

Temporal. 
Parietal. 

Frontal. 

The  face  has  fourteen*  bones : 

(a)  Unpaired: 
Vomer. 

(6)  Paired: 

Nasals. 

Mandible. 

Maxillae. 

Lacrymals. 
Malars.    • 

Palates. 

Turbinates. 

The  Bones  of  the  Cranium.— The  Occipital  Bone. — 

This  is  situated  in  the  back  part  and  base  of  the  skull, 
is  flattened,  lozenge-shaped,  bent  on  itself,  presenting 
an  internal  or  cerebral  surface,  which  is  concave,  and 
an  external  or  posterior  surface,  which  is  convex;  four 
borders  and  four  angles.  Below  and  in  front  the 
bone  shows  a  large  oval  opening,  called  the  foramen 
magnum,  for  the  passage  of  the  spinal  cord  and  mem- 
branes, spinal  accessory  nerves,  and  two  vertebral 
arteries.  On  either  side  of  the  anterior  boundaries 
of  the  foramen  magnum  are  two  condyles  which 
articulate  with  the  atlas  (first  cervical  vertebra). 
Anteriorly  a  rough  process  of  bone  (the  basilar)  artic- 
ulates with  the  body  of  the  sphenoid  and  temporal, 
and  the  posterior  border  of  the  occipital  bone  articu- 
lates with  the  parietal  Bones  on  either  side. 

The  Parietal  Bones. — These  are  paired  one  on  either 
side,  together  forming  the  median  portion  of  the  roof 


BONES  OF  THE  HEAD  61 

and  side^of  the  skull.  Each  is  roughly  quadrilateral, 
and  presents  two  surfaces — external  and  internal,  four 
borders  and  four  angles.  This  bone  articulates,  at 
the  anterior  border,  with  the  frontal  bone;  posterior 
border,  with  the  occipital  bone;  internal  border,  with 
opposite  bone;  inferior  border,  great  wing  of  sphenoid; 
squamous  portion  of  temporal,  and  the  mastoid  por- 
tion of  the  temporal. 

Fig.  26 


UGULAR    PROCESS 


The  occipital  bone,  viewed  from  below.     (Spalteholz.) 

The  Frontal  Bone. — ^This  forms  the  forehead,  and 
also  enters  into  the  roofs  of  the  orbital  and  nasal 
cavities.  Its  anterior  surface  is  convex  and  the  con- 
vexity is  greatest  on  either  side,  where  the  rounded 
frontal  eminences  are  to  be  seen,  separated  by  a  slight 
depression  below  from  the  superciliary  ridges.  The 
latter  ridges  are  just  above  the  orbits  and  afford  pro- 
tection to  them  from  injury.  In  the  middle  line  be- 
tween the  two  ridges  is  a  smooth  surface — the  glabella. 


62 


OSTEOLOGY 


The  orbital  arch  ends  in  extremities  called  the  internal 
and  external  angular  processes.  The  frontal  sinuses 
(hollow  spaces)  which  communicate  with  the  nasal 
cavities  contain  air,  and  are  lodged  in  the  frontal 
bone  just  above  the  orbital  arches.  The  frontal  bone 
articulates  with  twelve  bones  —  the  parietals,  the 
sphenoid,  the  malars,  the  nasals,  the  superior  maxillae, 
lacrymals,  and  ethmoid. 


Fig.  27 


if/l    Oppn," 


Sphenoid  of  temT>" 

Left  parietal  bone,  external  surface.     (After  Gray.) 


The  Temporal  Bones. — These  are  paired,  assist  in 
forming  the  sides  and  base  of  the  skull,  and  contain 
the  organ  of  hearing.  They  present  three  parts — 
squamous,  petromastoid,  and  tympanic. 


BONES  OF  THE  HEAD 


63 


The  Squamous  Portion. — ^This  is  scale-like  in  form 
and  very  thin.  Its  external  surface  is  convex,  smooth, 
and  affords  attachment  to  the  temporal  muscle  and 


Fig.  28 


,  ,  External 

anqidar  process.         ^^^^^^,  ^^,^^^ 

Nasal       spine. 
Frontal  bone.     Outer  surface.     (Gray.) 


bounds  part  of  the  temporal  fossa.  Proceeding  for- 
ward from  the  lower  part  of  this  portion  of  the  bone 
is  a  long  arched  process  of  bone,  the  zygoma  or  zygo- 
matic process. 


64 


OSTEOLOGY 


The  Petromastoid  Portion. — This  consists  of  the 
mastoid  portion,  the  thick,  conical  process  of  bone 
behind  the  external  opening  of  the  ear,  and  a  pyram- 
idal portion  called  the  petrous  portion,  forms  part  of 
the  floor  of  the  skull.    The  mastoid  portion  contains  on 


Fig.  29 


*  Mastoid 
foramen. 


DIGASTRIC. 


Auditonj^^f^stch^ 
process. 


Left  temporal  bone:     outer  surface.     (Gray.) 


section  a  number  of  cellular  spaces  communicating 
with  one  another,  called  the  mastoid  cells.  The 
mastoid  cells  open  into  the  middle  ear,  and  contain 
air.  They  are  lined  with  a  prolongation  of  mucous 
membrane  from  the  tympanum,  which  extends  into 
them  through  an  opening,  by  which  they  communicate 


BONES  OF  THE  HEAD  65 

with  the  ..cavity  of  the  tympanum.  The  petrous,  .pot 
tion  is  a  pyramidal  process  of  bone  wedged  in  at  the 
base  of  the  skull,  between  the  sphenoid  and  occipital 
bones.  It  has  a  foramen — internal  auditory — for  the 
passage  of  the  facial  and  auditory  nerves. 

The  Tympanic  Portion.— This  is  placed  in  front 
of  the  anterior  surface  of  the  petrous  portion.  It 
bounds  the  external  auditory  meatus  in  front,  below 
and  behind,  and  lodges  the  tympanic  membrane  (ear- 
drum) . 

The  glenoid  fossa  is  a  depression  formed  by  the  squa- 
mous part  of  the  temporal  and  behind  by  the  tym- 
panic portion.  It  is  covered  with  cartilage  (squamous 
portion)  and  articulates  with  the  condyle  of  the 
mandible. 

The  Sphenoid  Bone. — This  wedge-like  bone  is  placed 
across  the  base  of  the  skull  near  its  middle,  and  binds 
the  other  cranial  bones  together.  It  assists  to  form 
the  cavities  at  the  base  of  the  cranium,  orbits,  and  nasal 
fossa,  and  has  foramina  and  fissures  for  the  passage 
of  six  pairs  of  cranial  nerves.  It  consists  of  a  solid 
body  of  bone,  with  a  thin  pair  of  lesser  and  greater 
wings.  It  articulates  with  twelve  bones,  all  those  of 
the  cranium  and  five  of  the  face;  posteriorly,  with  the 
occipital  and  temporals;  anteriorly,  with  the  ethmoid, 
palatals,  frontal,  and  malars;  laterally,  with  the  tem- 
porals, frontal,  and  parietals ;  inf eriorly,  with  the  vomer 
and  palatals.  The  upper  surface  of  the  body  of  the 
sphenoid  supports  the  pituitary  body,  and  the  circular 
and  cavernous  sinuses,  the  latter  enclosing  the  internal 
carotid  artery. 

The  Ethmoid  Bone  (sieve-like). — This  projects  down 
between  the  orbital  plates  of  the  frontal,  and  enters 
into  the  formation  of  the  floor  of  the  anterior  cranial 
fossa,  the  orbital,  and  nasal  cavities.  It  is  a  very 
small,  frail  bone.  Its  upper  surface  lodges  the  olfactory 
bulb  and  portions  of  the  olfactory  tract.  The  fila- 
ments of  the  olfactory  nerve  (sense  of  smell)  pass 
5 


66 


OSTEOLOGY 


through  foramina  in  the  cribriform  plate  to  be  dis- 
tributed to  the  mucous  membrane  of  the  nasal  cavities. 
The  anterior,  middle,  and  posterior  ethmoidal  cells  are 
lodged  in  this  bone;  they  communicate  with  the  nasal 
cavities.  It  possesses  a  perpendicular  plate,  which 
forms  a  portion  of  the  nasal  septum  between  the  two 
nasal  cavities. 

Bones  of  the  Face. — The  Two  Nasal  Bones.^ — These 
form  the  bridge  of  the  nose.  They  are  very  small 
but  strong  considering  their  size. 

Fig.  30 

Frontal  simises. 
Crista  galli. 


Perpendic 
plate  of  etlt- 
moid. 

Space  for 

triangular 

cartilage 

of  septum. 

Vomer. 


'phenoidal  sinuses. 


Rostrum  <>f 
sphenoid. 

Palate  proces; 

Int.  pterygoid 
plate. 


Vomer  in  situ. 


The  Vomer. — This  is  a  thin  flat  bone  which  joins 
with  the  perpendicular  plate  of  the  ethmoid  bone,  and 


BONES  OF  THE  HEAD 


67 


septal  cartilage  to  complete  the  septum  between  the 
nasal  cavities.  It  articulates  with  the  sphenoid, 
ethmoid,  both  palates,  superior  maxillae,  and  with  the 
septal  cartilage  of  the  nose. 


Nasal  bone. 
Nasal  proc. 


ifra-orbital 
foramen. 


nasal  spine 


Fig.  31 


...  •> 


Nasal  and  lacrymal  bones  in  situ.     (Gray.) 


Lacrimal  bone. 


Orbital  surface. 
Infra-orbital 
groove. 


Artie,  with  malar 


Post,  dental 
canals. 


Maxillary 
tuberosity. 


The  Lacrymal  Bones. — These  bones  are  paired. 
They  are  very  small  and  thin,  found  at  the  anterior 
and  internal  part  of  the  orbit.  The  outer  surface  of 
this  bone  forms  with  the  lacrymal  notch  of  the  superior 
maxilla  the  orifice  of  the  nasal  duct.  (The  latter  is 
the  entrance  of  the  canal  for  the  passage  of  the  tears 
from  the  eye  to  the  nasal  cavity.) 

The  Maxillae  Bones.^ — They  are  paired,  irregular  in 
shape,  and  the  principal  bones  of  the  face,  each  sup- 
porting the  upper  teeth  of  one  side,  helping  to  form 


68  OSTEOLOGY 

the  floor  and  outer  walls  of  the  nasal  fossae  and  the 
hard  palate  or  roof  of  the  mouth,  in  conjunction  with 
the  palate  bone,  also  a  part  of  the  floor  of  the  orbit. 
It  contains  the  hollow  space  just  above  the  canine 
tooth,  called  the  antrum  of  Highmore.  The  latter 
communicates  with  the  nasal  chamber  and  is  frequently 
the  seat  of  inflammation.  This  bone  articulates  with 
its  fellow  of  the  opposite  side,  the  nasal,  lacrymal, 
frontal,  ethmoid,  palate,  malar,  vomer,  inferior  tur- 
binate, and  sometimes  the  sphenoid. 

The  Palate  Bones. — They  are  two  in  number  situated 
at  the  back  part  of  the  nasal  fossse;  they  are  lodged 
between  the  maxilla  and  the  pterygoid  processes  of 
the  sphenoid.  Each  bone  assists  in  the  formation  of 
the  floor  and  outer  wall  of  the  nasal  cavity,  roof  of  the 
mouth,  and  floor  of  the  orbit. 

The  Turbinated  Bones. — They  are  situated  one  on 
each  side  of  the  outer  wall  of  the  nasal  fossse.  Each 
consists  of  a  layer  of  thin,  spongy  bone,  curled  upon 
itself  like  a  scroll — hence  its  name,  turbinated 

The  Malar  Bone. — This  bone  is  quadrangular,  and  is 
situated  at  the  upper  and  outer  part  of  the  face.  It 
forms  the  prominence  of  the  cheek,  part  of  the  outer 
wall  and  floor  of  the  orbit,  and  part  of  the  temporal 
and  zygomatic  fossse.  It  articulates  with  the  frontal, 
sphenoid,  temporal,  and  the  maxilla. 

The  Mandible  or  Lower  Jaw. — This  is  the  largest  and 
strongest  bone  of  the  face.  It  consists  of  a  horizontal 
portion  called  the  body,  which  forms  the  chin,  and 
two  perpendicular  rami,  which  join  the  body  to  form 
the  angle  of  the  jaw.  It  articulates  by  its  condyles 
with  the  glenoid  cavity  of  the  tympanic  portion  of  the 
temporal  bone.  The  horizontal  portion  serves  for 
the  lodgement  of  the  lower  teeth. 

The  Hyoid  Bone. — ^This  is  a  bony  arch,  shaped  like 
a  horseshoe,  and  consisting  of  five  segments — a  body, 
two  great  cornua,  and  two  lesser  cornua.  It  is  situated 
in  the  neck  in  the  receding  angle  below  the  chin.    It  is 


BONES  OF  THE  HEAD 


69 


supported  by  the  stylohyoid  ligaments  attached  to  the 
lesser  cornua  of  each  side..  The  attachment  of  muscles 
help  to  hold  this  bone  in  position  and  acts  as  a  fixed 
point  for  the  muscles  of  swallowing  and  articulating. 
Below  it  is  attached  to  the  larynx  by  the  thyrohyoid 
membrane.  The  hyoid  bone  can  be  felt  just  above 
the  Adam's  apple  (pomum  Adami).  It  also  affords 
attachment  to  the  muscles  which  lower  the  jaw, 
depress  the  tongue,  and  aid  as  accessory  muscles  of 
respiration. 


Fig.  32 


Orbital  surface 


Infraorbital  groove 


Union  wit/i  lacrimal  bone 


Inferiorten/poral        ^ 

surface  ^    r\^       ~    ^,  _ 

Post,  dental  canals 


Maxillan/  tuberosity  -"-"^  ""^V-^ 
Zygomatic  process ' 


Frontal  process 

,  .Zammal  ?nar^in 

Infraorbital  margin 

^  Anterior  surface 

'Infraorbital  forajnen 

^,.' Canine  fossa 

' '  '^Palatine  process 

. . .  -Ant.  nasal  spine 
Aloeolar  process 


Right  upper  jaw  bone,  maxilla,  fi:om  without. 


The  Skull  as  a  Whole. — At  birth  the  skull  is  large 
in  comparison  with  the  other  parts  of  the  skeleton. 
The  face  is  small  and  equals  only  about  one-eighth 
of  the  bulk  of  the  cranium,  as  compared  to  the  size  of 
the  face  in  the  adult  which  equals  about  one-half  of 
the  size  of  the  skull.  Ossification  of  the  bones  of  the 
skull  in  the  infant  is  not  complete;  they  are  held  together 
by  membranous  tissue  and  these  intervals  between  the 
bones  are  termed  fontanelles.      There  are  six:   Two, 


70 


OSTEOLOGY 


anterior  and  posterior,  and  four,  an  anterolateral  and 
posterolateral  on  either  side. 


Fig.  33 


Skull  at  birth,  showing  the  anterior  and  posterior  fontanelles.     (Gray.) 
Fig.  34 


The  lateral  fontanelles.     (Gray.) 


The  anterior  fontanelle  is  the  largest  and  is  situated 
at  the  junction  of  the  sagittal,  coronal,  and  inter- 
frontal   sutures;   it   is   lozenge-shaped   and    measures 


PLATE    I 


Anterior  Aspect  of  the  Skull. 


PLATE   11 


kv.     t-'    v^ 


Lateral  Aspect  of  the  Skull. 


BONES  OF  THE  HEAD  71 

about  1^  inches  from  before  backward  and  1  inch 
from  side  to  side.  Pulsation  can  be  felt  over  this 
fontanelle  up  until  the  twelfth  to  twenty-fourth 
month.  It  usually  disappears  by  ossification  after  the 
second  year,  but  cases  have  been  reported  when  it 
persists  throughout  life. 

The  posterior  fontanelle  is  triangular  in  form  and 
is  situated  at  the  junction  of  the  superior  angles  of  the 
parietal  bones  with  the  occipital  bone.  The  lateral 
fontanelles  are  irregular  in  shape,  and  are  located  at 
the  antero-inferior  and  postero-inferior  angles  of  the 
parietal  bones  respectively.  The  posterior  and  lateral 
fontanelles  close  shortly  after  birth.  The  lack  of 
ossification  in  the  bones  of  the  skull  favors  the  over- 
lapping of  the  bones  or  moulding  of  the  infant's  head 
during  parturition,  thus  facilitating  delivery  and  pre- 
venting injury  to  the  mother  and  child;  of  course, 
barring  some  abnormal  condition  at  the  time  of  birth. 

In  adults  the  skull  bones  are  closely  fitted  by  uneven 
edges,  there  being  interposed  a  little  fibrous  tissue 
continuous  with  the  periosteum,  the  dentations  are 
confined  to  the  external  table,  the  edges  of  the  inner 
table  lying  in  apposition.  The  lower  jaw  has  a  mov- 
able articulation  differing  from  the  others. 

The  bones  forming  the  vertex  or  superior  surfaces 
of  the  skull  are:  frontal,  two  parietal,  two  temporal 
(squamous  and  mastoid  portions),  and  great  wing  of 
the  sphenoid. 

The  Orbital  Fossae  or  Orbits. — These  are  pyramidal 
in  shape,  with  their  bases  turned  forward  and  outward. 
They  are  just  below  the  supraorbital  arches;  their 
inner  walls  are  nearly  parallel  and  the  outer  walls 
diverge  at  slight  right  angles  to  each  other.  Each 
is  formed  by  seven  bones  or  eleven  for  the  two  orbits 
— the  frontal,  sphenoid,  ethmoid,  lacrymal,  palate, 
malar,  maxilla.  The  roof  of  each  is  formed  by  the 
orbital  plate  of  the  frontal  and  small  wing  of  the 
sphenoid;  the  floor,  by  the  malar,  maxilla,  and  orbital 


72  OSTEOLOGY 

plate  of  the  palate;  inner  wall,  by  the  nasal  process 
of  the  maxilla,  lacrymal,  ethmoid,  and  body  of  the 
sphenoid;  outer  wall,  by  the  malar  and  frontal  and 
great  wing  of  the  sphenoid. 

The  Nasal  Fossa  or  Cavities. — ^These  are  placed  one 
on  each  side  of  a  median  vertical  wall.  They  open  in 
front  by  the  anterior  nasal  apertm-e  (nares)  and  behind 
by  the  posterior  nares.  They  cominunicate  with  the 
sinuses  (air  spaces)  of  the  frontal,  sphenoid,  and  antrum 
of  Highmore,  the  latter  is  in  the  body  of  the  maxilla, 
and  the  ethmoidal  cells.  Thus  the  danger  from  infec- 
tion entering  these  air  spaces  following  an  abscess  for- 
mation, influenza,  etc.,  may  readily  be  understood. 


THE   VERTEBRAL   COLUMN    AS    A   WHOLE 

The  vertebral  or  spinal  column  is  a  central  axis  upon 
which  other  parts  are  arranged,  situated  in  the  median 
line  at  the  posterior  part  of  the  trunk;  above  it  sup- 
ports the  head,  by  having  the  first  vertebra  receive 
the  condyles  of  the  occipital  bone;  laterally,  the  ribs, 
and  it  rests  on  the  sacrum.  It  is  made  up  of  thirty- 
three  separate  vertebrae,  imposed  one  upon  the  other 
with  an  intervertebral  layers  of  cartilages  between 
each  one,  and  held  in  firm  relationship  by  means  of 
ligaments. 

The  vertebrae  are  divisible  into  seven  cervical, 
twelve  thoracic,  five  lumbar,  five  sacral,  and  four 
coccygeal.  The  cervical,  thoracic,  and  lumbar  verte- 
brae remain  separate  throughout  life,  and  are  known 
as  true  or  movable  vertebrae;  but  the  sacral  and  coccy- 
geal vertebrae  are  firmly  united  in  the  adult,  so  as  to 
form  two  bones — five  entering  into  the  formation  of 
the  sacrum  and  four  into  the  terminal  bone  of  the 
spine  or  the  coccyx.  The  sacral  and  coccygeal  verte- 
brae are  called  the  immovable  vertebrae. 

The  average  length  of  the  vertebral  column  is  about 


Fig.  35 


1st  cervical 
or  Atlas. 


Coccyx. 
Lateral  view  of  the  vertebral  column.     (Gray.) 


74  OSTEOLOGY 

twenty-six  to  twenty-seven  inches  measured  along  the 
curved  anterior  surface  of  the  column.  The  cervical 
part  measures  about  five,  the  thoracic  about  eleven  or 
twelve,  the  lumbar  about  seven  inches,  and  the  sacrum 
and  coccyx  the  remainder. 

Viewed  from  the  side  it  presents  several  curves. 
The  cervical  curve  commences  at  the  odontoid  process 
of  the  second  vertebra,  and  ends  at  the  middle  of  the 
second  thoracic ;  it  is  convex  in  front,  but  not  as  marked 
as  the  other  curves.  The  thoracic  curve  is  concave 
forward,  commences  at  the  middle  of  the  second  thor- 
acic, and  ends  at  the  middle  of  the  twelfth  thoracic. 
The  lumbar  curve,  commences  at  the  middle  of  the 
twelfth  thoracic  and  ends  at  the  sacrovertebral  angle 
(about  the  junction  of  the  sacrum  with  the  fifth  lum- 
bar vertebra).  It  is  convex  in  front;  the  convexity 
being  more  marked  in  the  lower  three  lumbar  verte- 
brae. These  curves  and  convexities  are  formed  by  the 
bodies  of  the  vertebrae.  While  the  posterior  aspect  is 
formed  by  the  extending  spinous  processes  which  usually 
can  be  felt  underneath  the  skin  and  fascia,  no  matter 
how  stout  the  individual.  Laterally  the  column 
presents  the  transverse  processes.  The  spinal  cord, 
membranes,  origin  of  spinal  nerves,  and  blood-supply 
are  within  the  spinal  canal — formed  by  the  inter- 
vertebral fibrocartilage,  body,  and  arched  lamina  of 
the  vertebrae;  the  latter  fusing  posteriorly,  complete 
its  boundaries.  Posteriorly,  the  spinous  processes 
occupy  the  median  line,  in  a  depression  known  as  the 
vertebral  groove  running  along  the  middle  of  the 
back.  In  the  cervical  region  the  processes  are  short 
and  bifid,  sloping  backward  and  a  little  downward. 
The  seventh  cervical  is  the  most  prominent  and  can 
always  be  seen  and  felt  beneath  the  skin,  therefore  its 
name — vertebra  prominens.  The  thoracic  processes  are 
oblique  above,  more  oblique  in  the  middle,  and  below 
are  nearly  horizontal;  in  the  lumbar  region  they  are 
horizontal.    The  transverse  processes  of  the  atlas  are 


THE  VERTEBRAL  COLUMN  AS  A   WHOLE     75 

long;  of  the  axis,  short;  then  extending  in  size  until 
the  first  thoracic  is  reached,  thence  diminishing  to  the 
last  dorsal,  and  becoming  suddenly  much  longer  in  the 
lumbar  region. 

The  intervertebral  foramina  are  always  in  front 
of  the  articular  processes  excepting  those  of  the  atlas 
and  the  upper  ones  of  the  axis.  They  are  named  from 
the  upper  of  the  two  vertebrae  which  go  to  form  them, 
excepting  in  the  cervical  region,  where  there  are  eight, 
the  fissure  between  the  skull  and  atlas  being  called 
the  first.  The  spinal  canal  is  narrowest  in  those  por- 
tions having  the  least  motion,  viz.,  the  dorsal  and  sacral 
regions.  It  is  round  and  f  of  an  inch  in  diameter 
in  the  dorsal  region;  it  is  triangular,  with  the  apex 
behind,  in  the  cervical  and  lumbar  regions;  and 
largest  of  all  in  the  cervical  region.  The  cervical 
vertebrae  each  have  a  foramen  (costotransverse)  in 
their  two  transverse  processes  for  the  vertebral  artery. 


Fig.  36 


Anterior 
tubercle  of  trans- 
verse process. 
Foramen  for  vertebral 
artery. 
Posterior  tubercle  of 
transverse  process. 


Transverse 
process. 


Superior 

articular 

process. 

Inferior 

articular 

process. 


A  cervical  vertebra.     (Gray.) 


General  Characteristics  of  a  Vertebra. — A  typical 
vertebra  is  made  up  of  two  parts,  an  anterior  solid 


76 


OSTEOLOGY 


portion,  and  a  posterior  portion,  the  arch  or  neural 
canal.  The  arch  is  formed  by  two  pedicles,  and  two 
laminae,  supporting  seven  processes — viz.,  four  articular, 
two  transverse,  and  one  spinous.  Taking  a  typical 
vertebra — the  tenth  thoracic,  for  example.  The  body 
is  cylindric;  the  upper  and  lower  surfaces  are  flat, 
with   a   rim   around   the   circumference.     The   front 


Fig.  37 


Superior  articular  process. 


Demi-facet  for  head  of  rib. 


Facet  for  tubercle  of  rib. 


Demi-facet  for  head  of  rib. 
Inferior  articular  process. 


A  dorsal  vertebra.     (Gray.) 

and  sides  are  convex  from  side  to  side  and  concave 
from  above  downward.  The  back  is  slightly  concave 
from  side  to  side.  The  neural  arch  is  completed 
laterally  by  two  processes  of  bone  arising  from  the 
postero-external  aspect  of  the  body,  called  pedicles, 
and  the  latter  continue — as  lamina — behind,  where 
they  meet  to  complete  the  posterior  aspect  of  the  neural 
arch.     The  upper  and  lower  borders  of  the  pedicles 


THE  VERTEBRAL  COLUMN  AS  A   WHOLE     77 

form  intervertebral  notches,  which  complete,  with  the 
neighboring  pedicle  of  the  vertebra,  intervertebral 
foramina.  The  spinous  process  projects  backward 
from  the  junction  of  the  two  laminae.  The  transverse 
processes,  one  on  either  side,  project  outward  from 
the  arch  at  the  junction  of  the  pedicle  with  the  lamina. 
The  articular  processes,  two  superior  and  two  inferior, 
extend  upward  and  downward  respectively  at  the  point 
of  origin  of  the  transverse  processes. 


Fig.  38 


Tubercle 


Biugrahi  of  nedion  of  odontoid, 
process. 

Diagram  of  section  of 
liyaincid. 

Foramen  for 
vertebral  artery. 


Groove  for  vertebral  artery 
and  1st  cervical  nerie. 


Rudimentary  spinous  process.. 

First  cervical  vertebra  or  atlas.     (Gray.) 


The  Atlas  (First  Cervical  Vertebra). — ^This,  sometimes 
called  rotation  vertebra,  has  no  body  or  spinous 
process,  but  is  a  large  ring  with  articular  and  transverse 
processes.  The  posterior  part  of  the  ring  or  arch 
corresponds  to  the  neural  canal  of  the  other  vertebrse; 
the  anterior  part  is  occupied  by  the  odontoid  process 
of  the  axis  (second  cervical  vertebra).  This  first 
vertebra  and  its  relation  with  the  odontoid  process 
of  the  axis,  below,  and  its  superior  articular  surface 
receiving  the  condyles  of  the  occipital  bone,  held  in 
position  by  ligaments,  permits  the  head  to  rotate  and 
bend  forward  and  backward,  as  in  turning  the  head 
from  side  to  side,  and  in  nodding.  The  odontoid 
process  of  the  axis  is  held  in  position  by  a  transverse 


78 


OSTEOLOGY 


ligament  passing  posterior  to  it  and  attached  to  the 
tubercle  on  the  the  inner  surface  of  the  lateral  mass 
on  either  side  of  the  arch,  and  by  check  ligaments 
extending  from  the  apex  of  the  odontoid  process  to  the 
occipital  bone.  The  atlas  has  a  foramen  (the  costo- 
transverse) for  the  vertebral  artery  in  its  transverse 
process. 

Fig.  39 

Odontoid  process. 


Rough  surface  for  check  ligaments. 
Artiadar  surface  for  tramverse  ligament. 


Spinous  process.- 


Articiilnr  surface  foi 
atlas. 


Body. 

\  Transverse  p)  ocess. 
Inferior  articular  process. 
Second  cervical  vertebra  or  axis.     (Gray.) 


The  Axis  (Second  Vertebra). — This  possesses  a  strong, 
prominent  process,  tooth-like  in  form,  which  arises 
perpendicularly  from  the  upper  surface  of  the  body. 
The  body  in  front  overlaps  the  vertebra  below.  The 
tip  of  the  odontoid  process  affords  attachment  to  the 
check  ligaments  (see  Fig.  52,  page  109)  and  has  an 
articular  surface  anteriorly,  which  articulates  w^ith  the 
atlas,  and  an  articular  facet  behind  for  the  transverse 
ligament,  which  holds  it  firmly  in  position.  The  pedi- 
cles and  laminae  form  the  neural  arch  in  the  same 
manner  as  the  atlas  and  other  vertebrae.  The  spinous 
process  is  larger  than  the  one  of  the  atlas.  The  trans- 
verse processes  are  small,  and  are  perforated  by  the 
foramen  for  the  vertebral  artery. 


THE  THORAX  AS  A  WHOLE  79 

The  Sacram  and  Cocc3rx. — ^The  sacrum  and  coccyx 
are  the  result  of  the  fusing  of  the  lower  nine  vertebrae 
into  two  bones,  five  to  form  the  sacrum  and  four  the 
coccyx. 

The  sacram  is  much  larger  than  the  coccyx,  is 
located  between  the  two  iliac  bones,  articulating 
above  with  the  fifth  lumbar  vertebra,  below  with  the 
coccyx,  and  is  perforated  with  foramina  which  transmit 
the  spinal  nerves. 

The  coccyx  is  pyramidal.  Its  vertebrae  are  very 
rudimentary,  and  it  possesses  a  trace  of  the  neural 
arch  and  transverse  processes  of  the  typical  vertebra. 


THE  THORAX  AS  A  WHOLE 

The  thorax  is  an  osseocartilaginous  cage,  conical  and 
flattened  from  before  backward.  The  short  antero- 
posterior diameter  is  characteristic  of  man,  but  in  the 
lower  mammals  and  human  fetus  it  is  longer  than  the 
transverse  diameter.  The  posterior  surface  is  convex 
forward,  formed  by  the  twelve  thoracic  vertebrae  and 
back  part  of  ribs;  on  either  side  the  sulcus  pulmonalis 
is  formed  by  the  ribs  as  they  project  backward,  so 
that  the  weight  of  the  body  is  more  equally  distrib- 
uted around  the  vertebral  column.  The  anterior 
surface  is  flattened  and  slightly  convex,  is  formed  by 
the  sternum  and  costal  cartilages,  and  lies  at  an  angle 
of  20  or  25  degrees  with  the  posterior.  A  horizontal 
anteroposterior  diameter  taken  from  the  base  of  the 
ensiform  is  8  inches  (20  cm.);  the  transverse  at  the 
eighth  or  ninth  ribs  is  11  inches  (28  cm.);  the  vertical 
anteriorly  is  6  inches  (15.5  cm.);  and  posteriorly  is 
12  inches  (31.5  cm.).  The  lateral  surfaces  are  convex; 
formed  by  the  ribs,  separated  from  each  other  by  the 
spaces  (intercostal). 

The  superior  or  upper  opening  of  the  thorax,  the  inlet, 
is  reniform  in  shape,  being  broader  from  side  to  side 


80 


OSTEOLOGY 


than  before  backward.  It  is  bounded  behind  by  the 
first  thoracic  vertebra;  in  front,  by  the  upper  border 
of  the  sternum,  and  on  either  side  by  the  first  rib. 


Fig.  40 


*^— First  thoracic 


The  thorax.     Ventral  view.     (Gray.) 


It  slopes  downward  and  forward  so  that  the  anterfor 
boundary  is  on  a  lower  level  than  the  posterior.  The 
anteroposterior  diameter  is  about  2  inches    (5  cm.). 


THE  THORAX  AS  A  WHOLE  81 

and  the,  transverse  about  4  inches  (10  cm.)-  The 
parts  which  pass  through  the  upper  opening  are, 
from  before  backward  in  or  near  the  middle  line — the 
sternohyoid  and  sternothyroid  muscles,  the  remains 
of  the  thymus  gland,  the  trachea  (windpipe),  the 
esophagus  (gullet),  thoracic  duct,  inferior  thyroid 
veins,  longus  colli  muscle  of  each  side,  bloodvessels 
and  nerves. 

The  inferior  or  lower  opening  is  formed  by  the  twelfth 
thoracic  vertebra  behind,  by  the  twelfth  ribs  at  the 
sides,  and  in  front  by  the  eleventh,  tenth,  ninth, 
eighth,  and  seventh  costal  cartilages,  which  ascend 
on  either  side  to  form  the  subcostal  angle,  from  the 
apex  of  which  the  ensiform  cartilage  projects.  The 
lower  opening  is  wider  transversely  than  from  before 
backward.  It  slopes  obliquely  downward  and  back- 
ward, so  that  the  cavity  of  the  thorax  is  much  deeper 
behind  than  in  front.  The  diaphragm  closes  in  the 
opening  forming  the  floor  of  the  thorax,  and  has  passing 
through  it  the  inferior  vena  cava,  the  esophagus, 
and  vagi  nerves,  the  aorta,  thoracic  duct,  vena  azygos 
major,  and  sometimes  splanchnic  nerves. 

The  thorax  contains  the  lungs  and  their  pleurae, 
the  heart  and  its  pericardium,  the  aorta  and  branches, 
and  the  structures  mentioned  under  the  upper  opening, 
which  pass  through  it. 

The  female  thorax  differs  from  the  male  as  follows: 
general  capacity  is  less,  sternum  is  shorter,  the  upper 
margin  of  the  sternum  is  on  a  level  with  the  lower 
part  of  the  body  of  the  third  thoracic  vertebra  (in  the 
male  it  is  the  body  of  the  second  thoracic  vertebra), 
the  upper  ribs  are  more  movable,  and  thus  allow  a 
greater  expansion  of  the  upper  part  of  the  thorax  than 
in  the  male  (Gray) . 

The  Sternum  or  Breast  Bone. — This  is  a  flat,  narrow 

bone,  situated  in  the  median  line  of  the  front  of  the 

chest,  and  in  the  adult  consists  of  three  portions.    It 

is   likened   to   an   ancient   sword;   the   upper    piece, 

6 


82 


OSTEOLOGY 


representing  the  handle,  is  called  the  manubrium; 
the  middle  and  larger  portion,  which  resembles  the 
blade,  is  the  gladiolus;  and  the  inferior  piece,  which 
resembles  the  point  of  the  sword,  is  called  the  ensiform. 

The  Ribs  (Costse). — There  are  twelve  pairs,  one  on 
each  side.  They  are  obliquely  placed,  running  forward 
and  downward.  The  obliquity  increases  from  above 
downward  to  the  ninth  rib,  when  it  reaches  the 
maximum;  from  this  point  downward  it  decreases. 

The  first  seven  pairs,  attached  by  costal  cartilages 
to  the  sternum,  are  called  sternal,  true,  or  vertebro- 
sternal ribs,  the  remaining  lower  five  pairs  are  asternal 
or  false  ribs;  each  of  the  upper  three  pairs  of  false 
ribs  has  its  cartilage  attached  to  the  cartilage  above 
it,  and  are  called  vertebrochondral  ribs;  the  last  two 
pairs  are  attached  to  the  vertebra  behind  and  their 
anterior  extremity  is  free;  they  are  called  floating  or 
vertebra^ribs. 


Fig.  41 


For  anterior  costotransverse  ligame 

Facet  for  body  of 
upper  thoracic  vertebra. 
Ridge  for  inter- 
articular  ligament.'^  ^tZwrratm 
Facet  for  body  of. 
lower  thoracic  vertebra. 

For  transverse  process 
lower  dorsal  vertel 


For  posterior  costotransverse  ligament. 


Vertebral  extremity  of  a  rib;  external  surface.     (Gray.) 


A  Typical  Rib. — Each  rib  has  an  anterior  and  pos- 
terior extremity.  The  anterior  extremity  is  hollowed 
into  a  pit  for  union  with  the  costal  cartilage.  The 
posterior  extremity  is  divided  into  a  head,  a  neck,  and 
a  tuberosity.  The  head  has  an  upper  and  lower  artic- 
ular facet  for  articulation  with  the  two  vertebrae, 
above  and  below;  and  between  the  two  facets  a  ridge 
for  the  attachment  of  the  interarticular  ligament. 


THE  THORAX  AS  A  WHOLE  83 

The  first  rib  is  the  shortest,  most  curved,  and  the 
broadest,  the  eighth  the  longest,  after  which  they 
decrease  in  length  to  the  twelfth;  the  twelfth  is  the 
narrowest. 

The  Peculiar  Ribs. — The  first  rib  is  short,  curved, 
and  not  twisted.  Its  surfaces  look  upward  and  down- 
ward. Head  is  small;  neck  is  slender  and  rounded; 
angle  coincides  with  the  tuberosity,  which  is  strong 
and  placed  on  the  outer  margin  of  the  rib.  The  upper 
surface  presents  close  in  front  of  the  tuberosity  a 
rough  impression  for  the  scalenus  medius  muscle,  and 
in  front  of  the  latter  two  smooth  impressions  with 
an  intervening  ridge;  the  posterior  impression  lodges 
the  third  portion  of  the  subclavian  artery,  the  ridge 
affords  attachment  to  the  scalenus  anticus  muscle,  and 
the  anterior  impression  receives  the  subclavian  vein. 

The  second  rib  is  not  twisted  and  has  no  angle;  it 
presents  near  its  middle  an  impression  for  the  scalenus 
posticus  muscle  and  two  serrations  of  the  serratus 
magnus. 

The  tenth  rib  has  but  one  articular  facet,  usually. 
The  eleventh  and  twelfth  ribs  are  short,  have  single 
articular  facets,  and  only  slight  elevations  to  mark 
the  tuberosities  which  do  not  articulate  with  the  trans- 
verse processes  of  the  vertebrae.  They  are  pointed 
anteriorly.  The  eleventh  has  a  slight  subcostal  groove; 
the  twelfth  has  no  angle. 

There  may  be  thirteen  ribs.  The  twelfth  rib  measures 
from  1  to  8  inches. 

The  Costal  Cartilages. — These  prolong  the  ribs  to 
the  sternum  and  increase  the  elasticity  of  the  thorax. 
They  consist  of  white  hyaline  cartilage.  The  first 
seven  pair  connect  the  ribs  and  sternum,  the  next 
three  pair  with  the  lower  border  of  the  cartilage  of  the 
preceding  rib.  The  cartilages  of  the  last  two  ribs 
(floating)  have  pointed  extremities  which  terminate 
in  free  ends.  They  increase  in  length  from  the  first 
to  the  seventh,  then  gradually  diminish  to  the  last. 


84  OSTEOLOGY 

They  have  an  anterior  and  posterior  surface,  and  a 
superior  and  inferior  border.  Their  articulations  with 
the  sternum  and  ribs  are  fixed  by  attached  ligaments. 


THE   BONES    OF   THE   UPPER   EXTREMITY 


c,,      ,  ,        .J,       /Clavicle  (collar  bone). 
Shoulder  girdle    [q^^^^^^  (shoulder  blade). 


Upper  limb 


Arm  (brachium,  humerus  (arm  bone). 

Forearm  (antebrachium,  radius,  ulna  (forearm  bones). 

(Carpus  (wrist  bones). 
Metacarpus  (bones  of  palm). 
Phalanges  or  bones  of  digits  (fingers) . 

The  Clavicle. — This  bone  forms  the  anterior  por- 
tion of  the  shoulder  girdle.  It  is  a  long,  thin  bone, 
curved  somewhat  like  the  letter  /,  and  placed  nearly 
horizontally  at  the  upper  and  anterior  part  of  the 
chest,  immediately  over  the  first  rib.  Its  inner  or 
sternal  end  articulates  with  the  upper  border  of  the 
sternum,  and  its  outer  or  acromial  end  unites  with 
the  acromion  process  of  the  scapula^  the  two  together 
connect  the  upper  limb  with  the  trunk  by  means  of 
ligaments. 

The  Scapula  (Shoulder-blade). — ^This  is  a  large,  flat 
bone,  situated  at  the  back  and  outer  aspect  of  the  chest, 
between  the  second  and  seventh  ribs.  Its  posterior 
border  is  about  1  inch  from  and  parallel  with  the 
vertebral  spines.  It  is  attached  to  the  trunk  by  the 
clavicle,  fascia,  and  muscles;  and  from  it  is  suspended 
the  humerus  by  means  of  the  capsular  ligament  of  the 
shoulder-joint,  which  is  attached  to  the  margins  of 
the  glenoid  cavity  and  the  head  of  the  humerus. 

This  bone  consists  of  a  large,  flattened,  triangular 
body,  two  processes,  the  coracoid,  and  spine,  which 
ends  in  the  acromial  process,  and  at  the  apex  a  cavity 
— glenoid,  for  articulation  with  the  head  of  the  humerus. 


THE  BONES  OF  THE  UPPER  EXTREMITY     85 

The  Humerus  (Arm  Bone). — This  bone  extends 
from  the  shoulder  to  the  elbow.  It  is  divided  into  a 
shaft,  and  an  upper  and  lower  extremity. 

The  Upper  Extremity. — ^This  includes  the  head,  a 
neck,  greater  and  lesser  tuberosities.  The  head  is 
directed  upward  and  slightly  backward,  and  makes 
an  angle  of  140  degrees  with  the  shaft.  The  head  is 
round  and  articulates  with  the  glenoid  cavity  of  the 
scapula,  being  held  in  apposition  by  the  ligaments  of  the 
shoulder-joint.  Below  the  head  is  a  depression  pass- 
ing around  the  bone  called  the  anatomical  neck.  The 
great  tuberosity  is  an  eminence  of  bone  situated  on 
the  outer  and  anterior  aspect  of  the  bone  below  the 
anatomical  neck.  It  gives  attachment  to  the  supra- 
and  infraspinatus  and  teres  minor  muscles,  which 
turn  or  rotate  the  shoulder-joint  and  arm  outward. 
Lying  internal  to  the  great  tuberosity  is  the  bicipital 
groove,  which  lodges  the  tendon  of  the  long  head  of  the 
biceps  muscle.  Internal  to  the  groove  is  another 
smaller  eminence  called  the  lesser  tuberosity;  it  receives 
the  tendon  of  the  subscapularis  muscle,  w^hich  rotates 
or  turns  the  shoulder- joint  inward. 

The  Shaft. — This  is  cylindrical  below  the  tuberosities 
(and  is  known  as  the  surgical  neck)  and  triangular 
below  this  portion.  It  is  divided  into  external,  internal, 
and  posterior  surfaces  by  anterior  and  lateral  borders. 
On  the  outer  border,  near  the  middle,  is  a  rough 
surface  of  bone  called  the  deltoid  eminence;  it  affords 
attachment  to  the  deltoid  muscle.  The  middle  of  the 
inner  border  receives  the  coracobrachialis  muscle; 
the  lower  three-fourths  of  the  anterior  aspect  of  the 
shaft  is  covered  by  the  origin  of  the  brachialis  anticus 
muscle.  The  inner  and  outer  borders  become  sharp 
at  the  lower  third,  and  are  called  the  supracondylar 
ridges.  The  posterior  surface  of  the  shaft  is  twisted 
so  that  the  upper  part  looks  inward,  its  lower  part 
backward  and  outward.  Its  entire  surface  is  almost 
entirely  covered  by  the  origin  of  the  inner  and  outer 


86 


OSTEOLOGY 


heads  of  the  triceps  muscle,  except  a  portion  of  bone 
in  the  internal  aspect  of  the  surgical  neck,  and  a  narrow, 


m 


MUSCULO- 
SPIRAL  GROOVE 


SMALL 
TUBEROSITY 


iURGICAL 
NECK 


EXTERNAL. 
CONDYLE 


INTERNAL 
CONDYLE 


The  right  humerus,  front  view.     (Testut.) 


THE  BONES  OF  THE  UPPER  EXTREMITY     87 

groove  passing  obliquely  from  within  downward  and 
outward  between  the  two  portions  of  this  muscle, 
which  is  called  the  musculospiral  groove  and  lodges  the 
musculospiral  nerve  and  superior  profunda  artery. 

The  Lower  Extremity. — This  is  divided  into  an  inter- 
nal and  external  condyle,  an  articular  surface  sub- 
divided into  the  trochlea  and  capitellum.  The  condyles 
are  rounded  eminences  of  bone  extending  out  beyond 
the  borders  of  the  bone  and  can  be  always  felt  just 
beneath  the  skin.  Between  the  two  condyles  is 
seen  the  articular  facets,  the  outer — the  capitellum — 
is  round  and  smooth  and  articulates  with  the  cup- 
shaped  surface  of  the  head  of  the  radius;  the  inner — 
the  trochlea — presents  a  deep  depression  between  two 
well-marked  borders  and  articulates  with  the  sigmoid 
cavity  of  the  ulna.  These  articular  surfaces  mentioned 
enter  into  the  formation  of  the  elbow-joint,  and  are 
held  in  position  by  the  capsular  and  internal  and  exter- 
nal lateral  ligaments  of  the  elbow-joint.  Above  and 
in  front  of  the  articular  surface  (trochlea)  is  a  depres- 
sion called  the  coronoid  fossa,  which  receives  the  coro- 
noid  process  of  the  ulna  when  the  arm  is  flexed ;  above 
and  behind  the  trochlear  surface  is  a  deep,  triangular 
depression,  called  the  olecranon  fossa,  which  receives 
the  olecranon  process  of  the  ulna  when  the  forearm  is 
extended. 

The  Bones  of  the  Forearm.— The  Ulna. — ^This  is 
the  internal  of  the  two  bones  of  the  forearm.  It 
articulates  above  with  the  humerus,  externally  with 
the  radius,  and  below  the  triangular  fibrocartilage  at 
the  wrist.  It  presents  an  upper  and  a  lower  extremity 
and  a  shaft. 

The  Upper  Extremity. — It  is  divided  into  an  olec- 
ranon process,  a  coronoid  process,  and  greater  and 
lesser  sigmoid  cavities.  The  olecranon  process  forms 
the  uppermost  part  of  the  ulna.  It  terminates  supe- 
riorly in  front  in  a  peak  of  bone,  which  overhangs  the 
greater  sigmoid  cavity;  behind  this  is  a  rectangular. 


88 


OSTEOLOGY 


thickened  tuberosity,  which  forms  the  point  of  the 
elbow,  and  can  be  felt  just  beneath  the  skin.     The 


Fig.  43 


POSTERIOR 
BORDER 


POSTERIOR 
ORDER 


The  bones  of  the  right  forearm,  rear  view.     (Testut.) 


posterior  surface  of  the  olecranon  is  triangular  and 
becomes  narrowed  below  and  extends  into  the  posterior 
border  of  the  ulna.    The  anterior  surface  is  concave 


THE  BONES  OF  THE  UPPER  EXTREMITY     89 

and  smooth,  and  forms  the  upper  part  of  the  greater 
sigmoid  cavity.  The  inferior  surface  is  smooth  and 
attached  to  the  shaft.  The  greater  sigmoid  cavity 
articulates  with  the  trochlear  surface  of  the  humerus. 
The  coronoid  process  is  less  marked  than  the  olecranon 
process;  it  is  smooth,  concave,  and  forms  the  base  of 
the  greater  sigmoid  cavity. 

The  lesser  sigmoid  cavity  is  seen  at  the  outer  margin 
of  the  greater  cavity,  with  which  it  is  continuous;  it 
is  concave  from  before  backward;  and  articulates  with 
the  head  of  the  radius  held  in  position  by  the  orbicular 
ligament. 

The  Shaft. — The  shaft  tapers  from  above,  is  three- 
sided  in  its  upper  three-fourths,  slender  and  cylindrical 
in  its  lower  fourth.  It  presents  anterior,  posterior, 
and  internal  surfaces,  and  anterior,  posterior,  and 
external  borders. 

The  Lower  Extremity. — This  presents  a  rounded 
head;  from  its  inner  and  back  part  the  styloid 
process  projects  downward,  giving  attachments  to 
the  internal  lateral  ligament  and  the  triangular  fibro- 
cartilage  of  the  wrist-joint.  The  head  of  the  lower 
extremity  has  an  inferior  articular  surface,  upon  which 
the  triangular  fibrocartilage  plays,  and  an  outer,  nar- 
row one,  convex  for  the  sigmoid  cavity  of  the  radius. 
The  styloid  process  of  the  ulna  can  always  be  felt 
beneath  the  skin.  The  inner  border  of  the  ulna  has 
attached  to  its  length  the  interosseous  membrane,  a 
ligamentous  septum  stretching  to  the  radius. 

The  Radius. — It  lies  to  the  outer  side  of  the  forearm 
alongside  of  the  ulna.  It  is  a  long  bone,  and  articulates 
above  with  the  capitellum  of  the  humerus,  the  ulna, 
internally;  the  scaphoid  and  semilunar  bones  of  the 
wrist,  inferiorly.  It  presents  for  examination  a  shaft 
and  an  upper  and  lower  extremity. 

The  Upper  Extremity  or  Head. — It  is  disk- 
shaped,  convex  in  circumference,  and  its  upper  surface 
has  a  depression  for  the  capitellum  of  the  humerus, 


90 


OSTEOLOGY 


with  which  it  articulates.  It  also  internally  rotates 
within  the  lesser  sigmoid  cavity  of  the  ulna.  Below 
the  head  is  the  neck,  which  is  round  and  smooth,  and 
affords  attachment  to  the  supinator  brevis  muscle. 

The  Shaft. — It  is  larger  below  than  above,  slightly 
curved,  and  convex  outward  and  backward.  Below 
the  neck  on  the  inner  aspect  is  an  elevation  of  bone 
called  the  bicipital  tuberosity,  which  receives  the  tendon 
of  the  biceps  muscle.  Below  this  tuberosity  the  shaft 
has  three  surfaces  and  three  borders. 

The  Lower  Extremity.  —  On  the  inner  side  of 
the  lower  extremity  at  right  angles  to  the  inferior 
articular  surface  is  a  concave  articular  facet  which 
articulates  with  the  lower  extremity  of  the  ulna;  the 
two  are  held  together  by  ligaments  of  the  inferior 
radio-ulnar  articulation.  To  the  smooth  surface  of 
bone  between  these  articular  surfaces  is  attached  the 
interarticular  fibrocartilage  of  the  wrist-joint. 

The  Articulations  of  the  Carpal  Bones 


Scaphoid 

Semilunar 

Cuneiform 

Pisiform 

Trapezium 

Trapezoid 
Os  magnum 

Unciform 


Superior. 


Radius 

Radius 

Triangular 

fib.  cart. 

Free 

Scaphoid 

Scaphoid 

Scaphoid 
lunar 

Lunar 


External.        Inferior. 


Internal. 


Free  Trapezium 

trapezoid 

Scaphoid  Os  magnum 
unciform 

Semilunar       Unciform 


Free 
Free 


Free 


I   First  meta- 
carpal 

Trapezium  Second  meta- 
carpal 
Trapezoid  [Second,  third, 
and  fourth 
metacarpals 
Os  mag-        Third  and 
num         fourth  meta- 
carpals 


Oa  magnum 
semilunar 
Cuneiform 

Free 

Free 

Trapezoid 
second  met- 
acarpal 
Os  magnum 

Unciform 


Cuneiform 


Ante- 
rior. 

Pos- 
terior. 

Free 

Free 

Free 

Free 

Pisi- 
form 
Free 

Free 

Free 

Cunei- 
form 
Free 

Free 

Free 

Free 

Free 

Free 

Free  j 

Num- 
ber. 


The  Bones  of  the  Wrist  (Carpus).— The  bones 
of  the  wrist,  eight  in  number,  are  arranged  in  two 
rows.    Those  of  the  upper  row,  enumerated  from  the 


THE  BONES  OF  THE  UPPER  EXTREMITY     91 

radial  (outer  side)  to  the  ulnar  (inner  side),  are:  the 
scaphoid,  semilunar,  cuneiform,  and  pisiform;  those  of 
the  lower  row,  enumerated  in  the  same  order,  are: 


Scaphoid-,,^ 
Os  magnum  - . 
Trapezium 
Trapezoid-. 

Netacan 


Fig.  44 
Bones  of  wrist 


Semilunar 

■Cvneifo?yn. 

...Fi si  form 

Unciform 


PhalanzTE' 
FhalanxM 


Bones  of  the  hand. 


the  trapezium,  trapezoid,  os  magnum,  and  unciform. 
Each  bone  presents  six  surfaces — superior,,  inferior, 
anterior,  posterior,  internal,  and  external.  The  anterior 
and  posterior  are  rough  for  the  attachment  of  ligaments. 


92  OSTEOLOGY 

The  Metacarpal  Bones  or  Bones  of  the  Pahn. — 
The  metacarpal  bones  are  five  in  number,  from  1  to  5, 
the  first  being  the  metacarpal  bone  of  the  thumb,  the 
fifth  the  metacarpal  bone  of  the  little  finger.  They 
are  long,  cylindrical  bones  presenting  a  shaft,  and  an 
upper  and  lower  extremity. 

Articulations  of  Metacarpal  Bones. — 

First  bone  (proximal  extremity)  trapezium. 

Trapezium,  trapezoid,  os  mag- 
Second  bone  (proximal  extremity)  •      num. 

Third  metacarpal  bones. 

Third  bone  (proximal  extremity)      (Os  magnum    second  and  fourth 

1^     metacarpal  bones. 

Fourth  bone  (proximal  extremity)   (^'    TffT'    "^"^^°"^'  ^^^''^ 

[     and    fifth   metacarpal    bones. 

Fifth  bone  (proximal  extremity)       (Unciform     and     fourth     meta- 
^       \     carpal  bones. 

The  distal  extremity  of  each  metacarpal  bone  artic- 
ulates with  the  corresponding  proximal  extremity  of 
the  first  phalanx  below. 

The  Phalanges  of  the  Hand  (Four  Fingers,  One 
Thumb). — The  phalanges  are  fourteen  in  number, 
three  for  each  finger  and  two  for  the  thumb.  They 
consist  of  a  shaft  and  upper  and  lower  extremity. 
They  are  similar  in  shape  to  the  metacarpal  bones, 
only  smaller,  and  are  held  together  by  ligaments,  re- 
inforced by  the  fibrous  sheaths  of  the  flexor  and  exten- 
sor tendons.  The  first  bone  articulates  with  its  meta- 
carpal bone  above,  and  the  second  phalanx  below; 
the  second  with  the  first  or  proximal  phalanx  above 
and  the  third  or  distal  phalanx  below;  and  the  third 
phalanx  with  the  second  phalanx  above.  Of  course, 
the  first  phalanx  of  the  thumb  articulates  with  the 
metacarpal  bone  above  and  the  second  phalanx  below; 
the  second  phalanx  articulates  with  the  first  phalanx 
above;  there  being  no  third  phalanx. 

All  the  long  bones  described  have  a  nutrient  canal 
for  the  entrance  of  the  nutrient  artery. 


Lower 
limb 


THE  BONES  OF  THE  LOWER  EXTREMITY     93 


THE  BONES  OF  THE  LOWER  EXTREMITY 


Pelvis          Ossa  innominate  (with  sacrum  and  coccyx) 
Thigh  Femur 

f  Tibia 

\  Fibula 

{Tarsus 
Metatarsus 
Phalanges  (toes) 


Leg 


The  Bones  of  the  Pelvis. — The  Os  Innominatum 
(Hip  Bone). — This  is  so  named  from  its  bearing  no 
resemblance  to  any  known  object.  There  is  one  on 
either  side.  It  is  irregular  in  shape,  twisted,  flat  above, 
expanded  below,  and  constricted  in  the  centre.  With 
its  fellow  of  the  opposite  side  it  forms  the  lateral  and 
anterior  walls  of  the  pelvic  cavity,  which  is  completed 
behind  by  the  sacrum.  In  young  subjects  it  consists 
of  three  separate  parts  that  meet  to  form  the  large 
bone,  and  for  purposes  of  description  is  divided  into 
the  ilium,  ischium,  and  pubis. 

The  ilium  is  the  upper  expanded  portion  and  forms 
less  than  two-thirds  of  the  acetabulum  (this  is  the 
cavity  which  receives  the  head  of  the  thigh  bone). 

The  OS  pubis  forms  with  its  fellow  of  the  opposite 
side  the  anterior  wall  of  the  pelvic  cavity,  and  bounds 
the  thyroid  or  obturator  foramen  above  and  partly 
in  front.  It  consists  of  a  body  and  two  rami;  at  the 
inner  extremity  of  the  body  is  a  roughened  surface, 
oval  in  shape  for  articulation  with  the  opposite  bone; 
when  the  two  bodies  articulate  they  form  the  symphysis 
pubis.  The  ascending  and  descending  rami  pass  up- 
ward and  downward  respectively  from  the  body. 

The  ischium  forms  the  lower  and  back  part  of  the 
hip  bone,  bounds  the  thyroid  foramen  below,  and  forms 
over  two-fifths  of  the  acetabulum.  It  presents  a  body, 
a  ramus,  and  a  tuberosity. 

The  Pelvis  as  a  Whole. — The  pelvis  (basin)  is  com- 
posed of  four  bones:  two  ossa  innominata  (innominate 


94 


OSTEOLOGY 


bones)  on  either  side  and  in  front  and  the  sacrum  and 
coccyx  behind.  It  is  divided  by  an  oblique  Hne  passing 
through  the  prominence  of  the  sacrum  behind,  and  the 
iliopectineal  line  and  symphysis  pubis  in  front,  into 
a  false  and  true  pelvis. 


Fig.  45 
if  OIL/ 


POSTERIOR    SUPE- 
RIOR   SPINE 


POSTERIOR 
FERIOR    SP 


SPINE    OF. 
ISCHIUM 
SMALL    SCIATIC 
NOTCH 


ANTERIOR    SUPE- 
RIOR   SPINE 


ANTERIOR     IN- 
FERIOR   SPINE 


*^«*IUM 

The  right  hip  bone;  outer  surface. 


(Testut.) 


The  False  Pelvis. — This  is  the  expanded  portion 
of  the  pelvic  cavity  above  this  plane.  It  is  bounded 
on  each  side  by  the  iliac  fossae  of  the  iliac  bones;  in 
front  it  is  incomplete;  the  space  of  the  basin  between 
the  anterior  superior  spines  is  completed  by  the 
abdominal  wall;  behind  is  a  deep  notch. 


THE  BONES  OF  THE  LOWER  EXTREMITY     95 

The  True  Pelvis. — This  is  the  real  bony  basin, 
situated  below  the  oblique  plane  which  divides  the 
prominence  of  the  sacrum,  iliopectineal  line,  and  sym- 
physis pubis.  It  is  smaller  than  the  false  pelvis.  For 
description  it  presents  a  superior  circumference  or  inlet, 
an  inferior  circumference  or  outlet,  and  a  cavity.  The 
superior  circumference  forms  the  brim  of  the  pelvis, 
the  heart-shaped  space  being  called  the  inlet. 


Fia.  46 


Oyst  of  ilium 
Sup.  spine  of 


Inf.spini 

Obturator  fo/a/m/f,  \^ 
Body  of  /sc/iiufn^ 
fuberosity  of  ischium. 

Ramus  of  ischium 

Body  of  pubic  bone . 


Great  S aero  sciatic 
notch 

.  Acetabulum 


'Cocci/x 


-Spine  of  ischium 
•  Bamus  of  pubic  bone 
-Sym/fhysis  pubes 


Male  pelvis  from  in  front  and  below. 


The  cavity  of  the  true  pelvis  is  bounded  in  front  by 
the  symphysis  pubis;  behind  by  the  concavity  of  the 
sacrum  and  coccyx,  which,  curving  forward  above  and 
below,  contracts  the  inlet  and  outlet  of  the  canal; 
laterally  it  is  bounded  by  the  inner  surface  of  the 
ischium  and  that  part  of  the  ilium  which  is  below 
the  iliopectineal  line.  It  is  shallow  in  front,  measuring 
1^  inches  in  depth  at  the  symphysis,  Z\  inches  in  the 
middle,  and  4|  inches  posteriorly. 
**  The^lower  circumference  or  outlet  is  irregular  in  shape. 
Bounded  by  three  eminences  the  point  of  the  coccyx 
behind,  and  the  tuberosities  of  the  ischia  on  either  side. 
The  eminences  are  separated  by  three  notches:  one  in 


96 


OSTEOLOGY 


front,  the  pubic  arch  formed  by  the  rami  of  the  ischia 
and  pubes,  and  the  symphyses.  The  other  notches, 
one  on  each  side,  are  formed  by  the  sacrum  and  coccyx 


Fig.  47 


Grmr  rroc/ianter 


/[met  of  femur 


-Ant  intrr/r(?ckanfC2-ir  /ine 
Zfsscr  rroc^o/zrcr 


3  :f^%*  '¥:f^\  .-^^  tfiberosltij 
Ext,  tubefvsfti/ /  w0^^^  i^Bm 

Right  thigh  bone,  femur. 

behind,  the  ischium  in  front,  and  the  ihum  above;  the 
latter  notches  are  called  the  sacrosciatic  notches;  in 
the  recent  state  they  are  converted  into  foramina  by 
the  lesser  and  greater  sacrosciatic  ligaments.    When  the 


THE  BONES  OF  THE  LOWER  EXTREMITY     97 

ligaments  are  present,  as  in  life,  the  real  boundaries  of 
the  outlet  are  the  subpubic  ligament  and  the  rami  of 
the  OS  pubis  and  ischium  in  front,  the  great  sacro- 
sciatic  ligaments  and  the  tip  of  the  coccyx  behind, 
and  the  tuberosities  of  the  ischia  on  each  side. 

The  Femur. — ^The  femur  (thigh  bone)  is  the  largest, 
longest,  and  strongest  bone  of  the  skeleton.  It  is  convex 
in  front  and  concave  behind,  and  when  the  body  is 
erect  the  femur  is  inclined  inward  and  slightly  back- 
ward. It  is  divisible  into  an  upper  and  lower  extremity 
and  a  shaft. 

The  Upper  Extremity.-^This  presents  a  head,  a  neck, 
and  a  great  and  small  trochanter.  The  head  is  joined  to 
the  shaft  by  the  neck,  it  is  round  and  forms  more  than 
a  half  sphere.  It  articulates  with  the  acetabulum  of 
the  innominate  bone.  Just  below  and  behind  the  centre 
of  the  head  is  a  depression  for  the  interarticular  or 
round  ligament  of  the  hip-joint,  which  is  attached 
by  its  upper  end  to  the  centre  of  the  acetabulum. 
The  neck  is  narrow  just  at  the  junction  of  the  head, 
constricted  in  the  centre,  and  widens  as  the  base  is 
approached;  is  flattened  slightly  anteriorly  and  poste- 
riorly, concave  above  and  below.  The  direction  of 
the  neck  is  slightly  upward,  forward,  and  inward, 
being  set  upon  the  shaft  at  an  angle  of  125  degrees. 
The  junction  of  the  neck  with  the  shaft  shows  in  front 
and  behind  a  slight  elevation  or  roughened  surface  of 
bone  called  the  anterior  and  posterior  intertrochan- 
teric lines,  and  they  afford  attachment  to  the  capsular 
ligament  and  ligament  of  Bigelow.  The  posterior 
intertrochanteric  line  in  the  middle  receives  the 
quadratus  femoris.  The  small  trochanter  is  a  small 
projection  of  the  bone  seen  at  the  inferior  aspect  of 
the  base  of  the  neck  when  it  unites  with  the  shaft. 
The  great  trochanter  is  a  projection  of  bone  extending 
upward  beyond  the  neck.  It  can  be  felt  under  the  skin. 
It  is  quadrilateral  in  shape,  with  its  base  attached  to 
the  shaft  of  the  femur. 


98  OSTEOLOGY 

The  Shaft. — The  shaft  is  long  and  rounded  in  front 
and  on  the  sides,  is  narrow  in  the  centre,  and  enlarges 
gradually  above  and  below,  being  the  broadest  at  the 
lower  extremity.  It  presents  an  anterior  surface, 
which  is  covered  by  a  flat,  yet  large  muscle  on  its 
upper  three-fourths  —  the  crureus  —  and  below  this 
two  small  spaces  of  bone  give  origin  to  the  subcrureus 
muscle.  There  are  an  internal  and  an  external  surface; 
they  are  covered  by  the  crureus  and  vastus  internus 
and  externus  respectively.  The  lateral  surfaces  are 
separated  posteriorly  by  a  longitudinal  rough  ridge  of 
bone,  about  the  middle  of  the  shaft — called  the  linea 
aspera.  It  is  divided  into  an  inner  and  outer  lip,  and 
a  middle  ridge. 

The  outer  and  inner  lips  of  the  linea  aspera  at  the 
junction  of  the  middle  with  the  lower  third  of  the  bone, 
posteriorly,  separate  and  include  between  their  diverg- 
ing borders  a  triangular-shaped,  smooth  surface  of 
bone,  free  from  muscular  attachments,  called  the  pop- 
liteal surface.  The  space  is  crossed  by  the  popliteal 
artery,  vein,  and  the  internal  popliteal  nerve,  the  artery 
being  next  to  the  bone. 

The  Lower  Extremity. — This  presents  two  condyles 
— internal  and  external  and  intercondylar  notch,  and 
an  inner  and  outer  tuberosity  or  tubercle.  The  con- 
dyles articulate  with  the  upper  articular  facets  of  the 
upper  extremity  of  the  tibia,  and  in  front  the  articula- 
ting surface  is  extended  upon  the  shaft  for  a  short 
space  (trochlear  surface),  to  articulate  with  the  patella 
(knee-cap).  The  capsular  ligament  of  the  knee-joint 
is  attached  just  above  the  condyles  on  the  shaft  of  the 
bone.  The  intercondylar  space  is  filled  with  fat  and 
has  the  crucial  ligaments  passing  from  the  internal 
surfaces  of  the  condyles  to  the  upper  surface  of  the 
tibia.  These  ligaments  as  they  cross  each  other  form 
the  letter  X.  The  femur  has  an  internal  and  external 
rounded  border. 


THE  BONES  OF  THE  LOWER  EXTREMITY     99 

The  Patella  or  Knee-cap. — This  is  a  flat,  triangular 
bone,  situated  at  the  anterior  part  of  the  knee-joint. 
It  is  usually  regarded  as  a  sesamoid  bone,  developed 
in  the  quadriceps  extensor  tendon  (formed  by  the 
rectus  femoris,  the  vastus  internus  and  externus,  and 
the  crureus  muscles). 

The  patella  can  always  be  felt  beneath  the  skin  and 
fascia. 


The  right  patella,  ventral  surface.     (Testut.) 


INNER        I 
BORDER      \ 


The  right  patella,  dorsal  surface.     (Testut.) 


Bones  of  the  Leg. — The  bones  of  the  leg  are  two, 
the  tibia  and  fibula. 

The  Tibia. — This  is  situated  at  the  inner  and  front 
part  of  the  leg.*;  It  is  the  longest,;  and  largest  bone 


100 


OSTEOLOGY 


in  the  body,  excepting  the  femur.     In  the  male  its 
direction  is  vertical;  in  the  female  inclined  obliquely 


OUTER   TU-k       S*^^^, 
STYLOID.       -^ 


ilNNER    TU- 
BEROSITY 


RNTERO-EXTER- 
NAL    BORDER 


m 


.ANTERIOR 
BORDER 


ANTERO-INTER- 
NAL    BORDER 


OUTER 
MALLEOLUS 


INNER 
MALLEOLUS 


The  right  tibitt  dnd  fibaia  in  ^heir  normal  r«l»tionff,  front  view, 
(Mod'fied  from  Tortut.) 


THE  BONES  OF  THE  LOWER  EXTREMITY     101 

downward  and  outward  slightly.  To  its  outer  side  is 
the  fibula. 

The  tibia  presents  an  upper  and  lower  extremity, 
and  shaft. 

The  Upper  Extremity  or  Head. — This  is  large 
and  expanded  on  either  side  into  the  internal  and 
external  tuberosities.  The  superior  surface  of  each 
tuberosity  presents  a  concave  articular  surface,  which 
receives  the  condyles  of  the  femur  above.  The  inner 
facet  is  oval,  the  outer  circular.  Posteriorly  the 
external  tuberosity  presents  a  facet  for  articulation 
with  the  head  of  the  fibula.  The  anterior  surfaces  of 
the  tuberosities  of  the  tibia  are  continuous  with  one 
another,  thus  forming  a  surface  which  is  triangular 
in  shape  and  at  the  lower  part  is  the  tubercle,  which 
receives  the  ligamentum  patellae. 

The  Shaft. — The  shaft  of  the  tibia  is  long  and  tri- 
angular, broad  above,  gradually  decreasing  in  size 
to  its  most  slender  part — the  commencement  of  the 
lower  fourth;  it  then  enlarges  again  at  its  lower  ex- 
tremity. It  presents  internal,  external,  and  posterior 
surfaces;  internal,  external,  and  anterior  borders,  the 
anterior  border  forms  the  shin,  so-called. 

The  Lower  Extremity. — This,  much  smaller  than 
the  upper,  presents  five  surfaces — anterior,  posterior, 
internal,  external,  and  inferior.  The  anterior  surface 
is  smooth  and  rounded  above,  and  crossed  by  the  ex- 
tensor tendons  of  the  toes  and  tibialis  anticus  muscle. 
The  external  surface  is  a  rough,  triangular  depression  for 
the  attachment  of  the  interosseous  membrane  above,  at 
its  lower  part  is  a  smooth  hollow  surface  covered  by  car- 
tilage, for  articulation  with  the  lower  end  of  the  fibula. 
The  inferior  surface  is  quadrilateral  and  articulates  with 
the  upper  aspect  of  the  astragalus,  one  of  the  tarsal 
bones;  this  surface  is  continuous  with  the  articular 
surface  of  the  internal  malleolus.  The  internal  surface 
is  practically  the  internal  malleolus,  a  pyramidal  process 
of  bone,  flattened  from  without  inward.     The  inner 


102  OSTEOLOGY 

surface  is  convex  and  just  beneath  the  skin.  The  outer 
surface  of  the  malleolus  is  smooth  and  articulates  with 
the  astragalus  bone.  The  posterior  surface  is  flattened 
and  crossed  by  the  flexor  tendons  of  the  toes  and  the 
tibialis  posticus  muscle. 

The  Fibula. — The  fibula  (clasp)  or  peroneal  bone, 
nearly  equal  in  length  to  the  tibia,  is  the  thinnest  long 
bone  in  the  body.  It  lies  parallel  with  the  tibia  at  the 
outer  side  of  the  leg.  It  articulates  by  its  upper  ex- 
tremity with  the  outer  tuberosity  of  the  tibia,  by  its 
lower  extremity  with  the  astragalus.  The  two  articu- 
lating extremities  are  held  in  place  by  ligaments,  all 
entering  into  the  formation  of  the  superior  and  infe- 
rior tibiofibular  articulation.  The  inner  border  has 
attached  to  it  the  outer  edge  of  the  interosseous  mem- 
brane, stretching  between  the  til^ia  and  fibula.  The 
fibula  is  the  most  irregular  bone  in  the  body  as  its 
surfaces  and  borders  are  not  evenly  defined. 

The  outer  aspect  of  the  lower  extremity  is  subcuta- 
neous and  is  grooved  behind  for  the  lodgement  of  the 
tendons  of  the  peroneus  longus  and  brevis  muscles — 
the  latter  tendon  being  next  to  the  bone.  The  lower 
extremity  forms  the  external  malleolus. 

The  Bones  of  the  Foot. — The  bones  of  the  foot  con- 
sist of  three  divisions — the  tarsus,  metatarsus,  and 
phalanges  (toes). 

The  Tarsus.^ — This  consists  of  seven  irregular-shaped 
bones  held  in  position  by  ligaments  and  reinforced  by 
the  inserted  sheaths  of  the  tendons  of  muscles.  The 
bones  are,  viz.,  the  os  calcis  or  calcaneum,  astragalus, 
cuboid,  scaphoid,  internal,  middle,  and  external  cuneiform. 
The  OS  calcis  forms  the  heel,  and  is  the  largest  of  the 
seven  bones.  It  articulates  above,  with  the  astragalus; 
in  front,  with  the  cuboid.  It  presents  six  surfaces — 
superior,  inferior,  internal,  external,  anterior,  and  pos- 
terior. 

The  astragalus  or  ankle  bone  (talus)  receives  the 
weight  of  the  body  from  the  leg.    It  articulates  with 


THE  BONES  OF   THE  LOWER  EXTREMITY     103 

four  bones — the  tibia  above  and  internally;  the  fibula 
externally;  os  calcis  below,  and  scaphoid  in  front.  It 
belongs  to  the  irregular  group  of  bones. 


Fig.  51 


P/ta/a/ixJT. 


P/ialc/uxJ 


J//t.  Cf//i/ef'o/'m .  . . 
Nid.cujdeform  ... 
Ext.  cfinieform .... 

Kavicalar  l/o//e. . 
Astragalus 


7}/be7'ositfj  offift/i 
7// eta  tars  a  I  dc//(c 


Cul^oid  done 


Os  Caie/'s 


Bones  of  the  right  foot. 


104  OSTEOLOGY  ' 

The  Metatarsal  Bones. — The  metatarsal  bones  are 
five  in  number;  they  articulate  with  the  tarsal  bones 
behind  and  the  corresponding  phalanges  (1  to  5)  in 
front.  They  present  for  examination  a  shaft,  a  proximal 
extremity,  or  a  base ;  a  distal  extremity  or  head. 

The  first  bone  is  the  shortest  and  thickest,  the 
second  the  largest,  and  the  fifth  the  thinnest.  Each 
bone  has  a  nutrient  canal  on  its  plantar  surface. 

The  Phalanges  of  the  Foot  (Bones  of  the  Toes). — The 
phalanges  have  the  same  arrangement  and  shape  as 
those  of  the  fingers,  except  that  they  are  longer  and 
larger.  They  are  fourteen  in  number  for  each  foot, 
allowing  three  (1st,  2d,  and  3d)  for  the  second,  third, 
fourth  and  fifth  toes;  the  big  toe  has  two  (1st  and  2d). 

The  first  or  proximal  phalanges  articulate  with  the 
corresponding  metatarsal  bone  above  and  the  second 
phalanges  below.  The  second  phalanges  articulate 
with  the  corresponding  first  phalanges  above  and  third 
below.  The  last  or  distal  phalanges  articulate  with 
the  corresponding  second  phalanges  above. 


QUESTIONS 

1.  How  many  bones  enter  into  the  formation  of  the  body  skeleton? 

2.  Name  in  a  general  way  the  bones  which  are  included  under 
the  axial  skeleton.    Appendicular  skeleton. 

3.  How  many  auditory  ossicles  are  there? 

4.  Give  the  classification  of  bones? 

5.  Name  the  long  bones.     Short  bones.     Flat  bones.     Irregular 
bones. 

6.  Give  an  example  of  an  articular  eminence.    Articular  depres- 
sion. 

7    Name  two  varieties  of  non-articular  eminences.    Non-articular 
depressions. 

8.  Give  the  constituents  of  dried  bone. 

9.  Do  the  mineral  salts  predominate  in  the  bones  of  children  or 
adults? 

10.  Why  are  the  bones  of  children  more  elastic  than  those  of 
adults? 

11.  What  is  the  periosteum  of  a  bone? 

12.  Give  the  two  classes  of  bone  based  on  their  composition? 

13.  Wha    do  you  understand  by  the  medulla  of  a  bone?     Give 
contents. 


QUESTIONS  105 

14.  Name  the  two  varieties  of  marrow  and  what  makes  the 
difference  in  color? 

15.  Give  the  function  of  bone-marrow. 

16.  How  are  bones  nourished  during  life? 

17.  Name  the  number  of  bones  forming  the  cranium.     The  face. 

18.  Name  the  unpaired  bones  of  the  cranium.    The  paired  bones. 

19.  Name  the  unpaired  bones  of  the  face.     The  paired. 

20.  Give  the  bones  bounding  the  orbital  cavity. 

21.  What  bones  and  cartilage  form  the  septum  of  the  nasal  cavity? 

22.  How  many  fontanelles  are  there  in  the  skull  of  an  infant? 

23.  Until  what  age  do  they  remain  membranous  before  ossifica- 
tion generally  occurs? 

24.  How  many  separate  vertebra  are  there? 

25.  Give  the  subdivisions  of  vertebra,  as  regards  their  location? 

26.  Name  the  movable  vertebra.     Immovable. 

27.  Mention  the  general  characteristics  of  a  typical  vertebra. 

28.  Give  the  contents  of  the  spinal  canal. 

29.  Name  the  structures  that  pass  through  the  upper  opening 
of  the  thorax.    The  lower  opening. 

30.  What  structure  separates  the  thoracic  cavity  from  the  abdomi- 
nal cavity? 

31.  What  openings  are  found  in  the  diaphragm  and  what  passes 
through  each  one? 

32.  Differentiate  the  female  from  the  male  thorax. 

33.  How  many  pairs  of  ribs  are  there? 

34.  Give  the  classification  of  ribs  as  to  arrangement. 

35.  What  do  you  understand  by  the  true  or  vertebrosternal  ribs? 
The  false  or  asternal  ribs?  Vertebrochondral  ribs?  Floating  or 
vertebral  ribs? 

36.  W^hat  are  the  functions  of  the  costal  cartilages? 

37.  What  bones  form  the  shoulder  girdle? 

38.  Name  the  bones  of  arm.     Forearm.     Wrist.     Palm.     Fingers. 

39.  Name  the  bones  which  form  the  pelvis. 

40.  Differentiate  the  true  from  the  false  pelvis. 

41.  Name  the  thigh  bone.    Bones  of  leg.    Instep. 

42.  How  many  metacarpal  bones  are  there?     Phalanges? 

43.  W^hat  bones  does  the  humerus  articulate?  The  femur?  The 
Tibia?    The  ulna?    The  radius? 


CHAPTER  VI 
ARTICULATIONS  OR  JOINTS 

The  General  Structure  of  Joints. — The  bones  of 
the  human  body  are  held  in  movable,  immovable,  or 
mixed  relations  with  each  other,  depending  upon  the 
degree  of  action  required  in  the  various  movements, 
functions,  and  positions  assumed  by  the  body.  The 
parts  entering  into  the  formation  of  these  relations 
taking  place  between  bones,  comprise  a  joint  or  artic- 
ulation— they  are:  bones,  ligaments,  cartilage,  and  a 
synovial  membrane. 

Bones. — ^The  articular  portions  of  bones  are  enlarged 
to  form  a  joint  of  suitable  size,  so  that  muscles  passing 
over  the  joint  can  act  at  a  greater  angle.  The  layer 
of  bone  beneath  the  cartilage  entering  into  a  joint  is 
a  compact  articular  lamella. 

Cartilage. — There  are  three  varieties  of  cartilage — 
hyaline,  fibrocartilage,  and  yellow  elastic  (see  page 
51  for  description  of  cartilage).  The  fibrocartilage 
and  hyalin  are  utilized  in  the  structure  of  a  joint; 
the  former  where  slight  movement  and  great  strength 
are  required — as  between  vertebrae  and  the  pubic  bones 
of  the  pelvis;  the  latter  where  freedom  of  movement 
is  essential,  and  a  greater  surface  for  general  con- 
venience of  mutual  connection  is  demanded,  as  in  the 
shoulder-  and  hip-joints,  etc. 

Ligaments. — The  ligaments  connecting  the  immov- 
able joints,  such  as  the  bones  of  the  skull,  consist  of 
a  thin  layer  of  fibrous  membrane — called  sutural  liga- 
ments, and  have  a  layer  of  cartilage  interposed — as 
the  bones  of  the  base  of  the  skull. 


THE  GENERAL  STRUCTURE  OF   JOINTS      107 

The  ligaments  are  mainly  white  fibrous  tissue  of 
various  forms,  serving  to  connect  the  articular  surfaces 
of  bones;  and  the  fibers,  usually  arranged  in  parallel 
rows,  or  closely  interlaced  with  one  another,  present 
a  white,  shining,  silvery  surface,  when  seen  in  the 
recent  state.  Some  ligaments  contain  yellow  elastic 
tissue,  which  is  present  in  the  ligamentum  subflava — 
connecting  the  adjacent  arches  of  the  vertebrae  in  man. 

The  Synovial  Membrane. — This  is  a  thin,  delicate 
serous  membrane  arranged  like  a  short  white  tube, 
attached  by  its  open  ends  to  the  margins  of  the  artic- 
ular cartilages  and  covering  the  inner  surfaces  of  the 
various  ligaments,  so  that  along  with  the  cartilage  it 
completely  encloses  the  joint  cavity.  It  secretes  a 
viscid,  thick  fluid  like  the  white  of  an  egg — hence  its 
term  synovia — ^which  acts  as  a  lubricant  to  the  joint. 
The  membrane  is  composed  of  a  layer  of  endothelial 
cells  resting  upon  a  thin  layer  of  fibro-elastic  (sub- 
endothelial)  tissue.  There  are  three  varieties  of  syno- 
vial membranes — articular,  bursal,  and  vaginal. 

The  articular  is  found  in  a  freely  movable  joint.  It 
lines  the  capsule  and  the  non-articular  intracapsular 
portion  of  the  bones  which  enter  into  the  formation  of 
a  joint.  Some  of  these  membranes  contain  fat,  acting 
as  a  cushion  between  the  articular  surfaces. 

The  bursse  are  mucous — between  the  skin  and  bone 
(subcutaneous  synovial  bursse) ;  and  synovial — between 
muscles,  tendons,  and  bone  (subtendinous  synovial 
bursse) . 

Vaginal  synovial  membranes  are  sheaths  for  tendons. 
They  prevent  friction  and  with  their  secretion  lubricate 
the  tendons  as  they  move  within  the  sheath  in  carry- 
ing on  their  action. 

Some  joints  have  tendons  passing  through  their 
cavities  (the  knee-joint  has  the  popliteus  muscle  and 
the  shoulder-joint  the  biceps)  and  they  are  always 
enclosed  by  the  synovial  membrane  within  the  joint, 
to  prevent  friction  and  facilitate  action. 


108 


ARTICULATIONS  OR  JOINTS 


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THE  CLASSIFICATION  OF  JOINTS 


109 


The  eiassification  of  Joints. — All  joints  of  the  body 
are  classified  under  three  main  groups  —  immovable 
articulation  (synarthrosis),  slightly  movable  or  mixed 
articulation  (amphiarthros),  movable  articulation  (diar- 
throsis). 


Fig.  52 


[CAPSULAR    LIQAMINT 

and  synovial 
I        membrane. 


..,..,*»     (capsular    LIOAMCNT 

ATLANTo- 1       ^^  synovial 
(        membrane.. 


Occipito-axial  and  atlanto-axial  ligaments.  Posterior  view,  obtained  by- 
removing  the  arches  of  the  vertebraj  and  the  posterior  part  of  the  skull. 
(Gray.) 


Synarthrosis  or  Immovable  Joint. — Under  this  classi- 
fication are  included  all  the  articulations  in  which 
the  surfaces  of  the  bones  are  in  almost  direct  contact, 
being  fastened  together  by  an  intervening  mass  of 
connective  tissue,  and  in  which  there  is  no  joint  cavity 
and  scarcely  any  motion.  Examples:  joints  between 
the  bones  of  the  skull  and  face,  excepting  those  of  the 
mandible. 

Amphiarthros  or  Mixed  Joint. — In  this  variety  there 
is  only  a  slight  amount  of  motion.  There  are  two 
varieties  —  symphysis,   as   the   symphysis   pubes   and 


no 


ARTICULATIONS  OR  JOINTS 


bodies  of  vertebrae  in  which  the  articulating  osseous 
surfaces  are  connected  by  a  broad  flattened  disk  of 
fibrocartilage  which  is  firmly  attached  to  both  bases 
in  the  articulation.  Syndesmosis,  in  this  variety  there 
is  slight  motion  and  the  bony  surfaces  are  held  in  rela- 
tion by  an  interosseous  ligament.  Example:  inferior 
tibiofibular  articulation  (between  tibia  and  fibula). 

Fig.  53 


Temporomandibular  articulation.     (Gray.) 


Diarthrosis  or  Movable  Joint. — Under  this  variety 
are  included  the  greater  number  of  the  joints  of  the 
body,  characterized  by  their  freedom  of  movement. 
These  joints  are  formed  by  the  bringing  together  of 
the  articular  surfaces  of  two  bones,  covered  by  hyaline 


THE  CLASSIFICATION  OF  JOINTS 


111 


cartilage,  and  held  together  by  ligaments  with  a  lining 
synovial  membrane. 

The  Kinds  of  Movement  Admitted  in  Joints. — 
These  are  divided  into  gliding,  angular,  circumduction, 
and  rotation.  They  are  often  combined,  and  it  is  sel- 
dom that  one  distinct  kind  of  motion  is  seen  in  any 
certain  joint. 

Fig.  54 


Temporomandibular  articulation.     Internal  view.     (Gray.) 


Gliding  Movement. — ^This  is  common  to  all  movable 
joints,  but  in  the  articulations  of  the  wrist  and  foot 
it  is  the  only  motion  permitted.  It  consists  of  one 
surface  of  a  bone  gliding  over  an  adjacent  bone  without 
any  angular  or  rotatory  movement.  The  sliding  of  a 
bone  over  a  wide  range  of  surface,  as  is  seen  in  the 
patella  (knee-cap)  over  the  condyles  of  the  femur,  is 
called  coaptation. 


112 


ARTICULATIONS  OR  JOINTS 


Angular  Movement. — ^This  is  seen  only  in  the  joints 
of  long  bones,  whereby  the  angle  between  the  two  bones 
is  either  increased  or  diminished.    It  is  expressed  in 


Fig.  55 


The  left  shoulder-joint,  scapuloclavicular  articulations,  and  proper  ligaments 
of  the  scapula.     (Gray.) 


four  ways,  as  follows:  bending  or  flexion — to  bend  the 
arm  or  leg  forward  or  backward,  etc. ;  straightening  or 
extension — to  straighten  the  legs  and  thighs  as  in  stand- 


THE  CLASSIFICATIONS  OF  JOINTS 


113 


ing,  the  arms,  fingers,  etc.;  adduction — to  move  a  limb 
toward  the  middle  line  of   the   body  or  extremity; 


Fig.  56 


Left  elbow-joint,  showing  anterior  and  internal  ligaments. 


abduction — to  move  it  away  from  the  middle  line  of  the 
body  or  extremity.     When  speaking  of  adduction  or 

8 


114 


ARTICULATIONS  OR  JOINTS 


abduction  of  the  fingers  or  toes,  the  second  finger  of  the 
hand  and  second  toe  are  taken  as  the  niiddle  line  and 
not  the  middle  of  the  body. 


Fig.  57 


ANTERIOR 

INTEHTRO' 

CHANTCRIC    LINE 


Right  hip-joint,  from  in  front.     (Spalteholz.) 


Circumduction. — ^This  is  the  limited  degree  of  motion 
which  takes  place  between  the  head  of  a  bone  and  its 
articular  cavity,  when  the  extremity  is  swung  in  such 
a  manner  that  the  sides  and  extremities  of  the  limb 
circumscribe  a   conical   space   around   an  imaginary 


THE  CLASSIFICATION  OF  JOINTS 


115 


axis,  the*  base  of  the  cone  corresponding  to  the  lower 
extremity  of  the  Hmb  and  the  apex  to  the  articular 
cavity.  This  kind  of  movement  is  best  seen  in  the 
shoulder-  and  hip-joints. 


Fig.  58 


Right  knee-joint.     Anterior  view.     (Gray.) 


Rotation. — ^This  is  the  movement  of  a  bone  upon  an 
axis,  which  is  the  axis  of  the  pivot  on  which  the  bone 
turns.    This  form  is  seen  best  in  the  rotation  between 


116  ARTICULATIONS  OR  JOINTS 

the  atlas  and  axis  when  the  odontoid  process  of  the 
axis  serves  as  a  pivot  around  which  the  atlas  turns. 

The  Apposition  of  Joint  Surfaces. — This  is  accom- 
plished by  (1)  atmospheric  pressure — as  in  the  hip- 
joint;  (2)  synovial  fluid;  (3)  ligaments  to  a  small 
extent;  (4)  muscles  to  the  greatest  extent.  A  short 
muscle  may  act  on  more  than  one  joint — the  gluteus 
maximus  extends  the  hip  and  also  the  knee  through 
its  insertion  into  the  fascia  lata. 

Note. — The  various  articulations  of  the  body  have 
not  been  described,  as  they  are  beyond  the  scope  of 
this  book.  However,  a  general  understanding  of  their 
attachment,  position,  and  the  bones  they  hold  together 
can  be  obtained  from  the  plates. 

QUESTIONS 

1.  Name  the  structures  which  enter  into  the  formation  of  a 
joint. 

2.  What  are  the  functions  of  ligaments? 

3.  Describe  a  synovial  membrane. 

4.  Give  the  varieties  of  synovial  membranes. 

5.  Do  joints  contain  a  fluid?     What  is  its  function?     Name? 

6.  Where    are    the    varieties    of    synovial    membranes    located 
usually? 

7.  Give  the  classification  of  joints  included  under  the  three 
main  groups. 

8.  Give  examples  of  an  immovable  joint  or  synarthrosis.  Mixed 
joint  or  amphiarthrosis.  Movable  joint  or  diarthrosis.  (See  Table 
of  Articulations.) 

9.  What  movements  are  admitted  in  joints  generally? 

10.  What  do  you  understand  by  flexion?  Extension?  Abduction? 
Adduction?    When  occurring  in  the  movements  of  a  joint? 

11.  By  what  means  are  joint  surfaces  held  in  apposition? 

12.  What  do  you  understand  by  the  terms:  Gliding  movement? 
Angular  movement?    Circumduction?    Rotation? 


CHAPTER  VII 
MUSCLE  TISSUE 

Myology  is  the  branch  of  anatomy  which  describes 
the  muscles — muscle  tissue. 

Muscle  tissue  consists  of  cellular  elements  arranged 
in  large  masses  to  form  muscles,  which  are  attached 
to  the  bones  of  the  body,  and  enter  into  the  structure 
of  numerous  organs  in  such  a  manner  that  by  their 
contraction  they  are  able  to  perform  the  various 
movements  of  the  body  and  functions  of  contained 
organs,  whether  of  a  voluntary  or  involuntary 
nature. 

Classification.  —  The  varieties  of  muscles  are: 
voluntary  striated,  involuntary  non-striated,  and  invol- 
untary striated. 

Voluntary  Striated. — These  muscles  are  characterized 
by  being  under  the  control  of  the  will,  also  called 
skeletal  muscles,  owing  to  their  attachment  to  bones 
which  they  move  and  assist  to  hold  in  position.  Each 
muscle  if  examined  microscopically  will  be  seen  to 
consist  of  a  number  of  fibers,  bound  together  by  white 
fibrous  tissue.  Each  fiber  is  a  long,  narrow  cylinder. 
It  varies  in  length  from  1  to  5  inches,  and  exhibits 
cross  and  longitudinal  striations.  The  composition 
of  each  fiber  is  a  number  of  small  fibers — called 
fibrillse,  surrounded  by  a  membrane — the  sarcolemma, 
and  separated  by  a  clear,  transparent  substance 
called  sarcoplasm,  and  many  peripherally  located 
nuclei.  The  sarcoplasm  represents  the  true  muscular 
substance.  The  longitudinal  striations  or  bands  seen 
are  formed  by  the  alteration  of  the  fibrillse  and  the 
sarcoplasm,  but  are  not  quite  as  distinct  as  the  crossed 


118 


MUSCLE  TISSUE 


band.    The  crossed  striations  are  due  to  the  change  in 
the  Hght  and  dark  disks  or  bands. 

The    sarcolemma    does    not   possess    the    inherent 
quality  of  contractility,  but  the  sarcoplasm  does. 


Fig.  59 


Fig.  60 


Part  of  a  fiber  of  cross-striped  muscular 
tissue,  showing  the  alternating  bands. 
(Gerrish.) 


Diagram  showing  the  minute 
structure  of  cross-striped 
muscular  tissue.     (Gerrish.) 


It  has  been  shown  that  the  fibrillar  form  the  fibers, 
the  latter  being  grouped  into  primary  bundles  called 
fasciculi,  and  these  primary  bundles  are  collected  into 
a  series  of  bundles  called  secondary  bundles,  and  groups 
of  the  latter  form  the  completed  muscle.  Each  muscle 
is  surrounded  by  a  sheath  of  white  fibrous  tissue  called 
the  epimysium,  which  gives  off  septa  or  layers  from 


CLASSIFICATION 


119 


its  under  surface  to  enclose  the  secondary  bundles  of 
fibers.  The  primary  bundles  receive  from  the  sheath 
surrounding  the  secondary  bundles  a  sheath  called 
the  perimysium.  The  latter  sends  fibers  that  pass 
between  the  individual  fibers  of  the  primary  bundle, 
called  the  endomysium. 


Fig.  61 


Fig.  62 


Fragment  of  a  fiber 
of  cross-striped  mus- 
cular tissue,  showing 
fibrils  separated  at 
one  end  by  teasing. 
(Gerrish.) 


Sheaths  of  muscular  tissue  in  cross-section- 
The  muscular  tissue  does  not  appear,  but  is  rep. 
resented  by  the  spaces  between  the  partitions. 
Outside  of  the  entire  muscle  is  epimysium; 
between  the  bundles  is  perimysium;  between  the 
fibers  is  endomysium — the  last  shown  in  two  areas 
at  the  right.    Diagrammatic.     (F.  H.  G.) 


The  bloodvessels  to  muscle  tissue  pierce  the  epi- 
mysium and  give  off  branches  which  follow  the  larger 
septa  between  the  bundles  until  the  perimysium  is 
reached  and  smaller  vessels  form,  which  pierce  the 
perimysium  to  form  longitudinal  capillaries;  the  latter 
anastomose  freely  with  each  other. 

The  lymphatics  are  not  numerous  and  are  sometimes 
wanting.  The  nerves  follow  the  bloodvessels  (see 
nerve  system — nerve  endings  (page  339). 

Voluntary  striated  muscles  are  found  attached  to 


120  MUSCLE  TISSUE 

the  skeleton  and  the  external  muscles  of  the  eye-ball, 
in  the  tongue,  the  pharynx,  upper  part  of  the  esophagus, 
anus,  diaphragm,  larynx,  and  external  ear. 

Involuntary  Non-striated,  Smooth  or  Visceral  Muscle. — 
It  is  not  under  the  control  of  the  will.  The  individual 
fibers  are  short,  narrow,  and  spindle-shaped.  Each 
fiber  is  surrounded  by  a  sheath,  but  it  is  not  a  sarco- 
lemma.  The  fibers  show  longitudinal  striation  at  the 
periphery  due  to  the  presence  of  fibrillse,  but  no 
transverse  striation.  There  is  only  one  nucleus,  which 
is  narrow,  elongated,  and  centrally  located. 

The  fibers  form  bundles,  but  instead  of  being  formed 
into  masses  like  the  voluntary  striated  variety,  they 
are  arranged  into  layers  which  extend  circularly, 
obliquely,  and  longitudinally  in  the  construction  of  the 
hollow  organs  of  the  body. 

Bloodvessels  are  arranged  as  in  the  former  variety. 

The  nerves  are  mostly  derived  from  the  sympathetic 
system. 

Non-striated  muscles  are  found  in  the  walls  of  the 
alimentary  tract,  extending  from  the  middle  third 
of  the  esophagus  to  the  anus,  in  the  ducts  of  glands, 
trachea,  and  bronchial  tubes,  the  ej^^-ball,  the  internal 
genito-urinary  apparatus,  walls  of  bloodvessels  (except 
the  heart)  and  lymphatic  system,  and  the  capsules  of 
some  organs. 

Involuntary  Striated  or  Cardiac  Muscle. — It  is  found 
in  the  muscle  of  the  heart.  The  fibers  are  short 
cylinders,  showing  striations,  but  no  sarcolemma.  A 
delicate  sheath  surrounds  the  fibers.  The  nucleus  is 
large,  oval,  and  placed  in  the  centre  of  a  zone  of  un- 
differentiated protoplasm,  filled  with  pigment  granules. 
There  are  seen  longitudinal  and  transverse  striations 
in  this  variety,  the  latter  being  fainter.  The  fibers  of 
this  variety  branch  and  join  with  the  branches  of  other 
muscle  cells. 

The   bloodvessels   are  derived   from   the   coronary 


THE  PROPERTIES  OF  MUSCLE  TISSUE       121 

arteries  and  small  branches,  are  in  intimate  relation 
with  the  fibers,  the  smaller  branches  running  parallel 
to  the  muscle  bundles  and  sometimes  lying  within 
them.  The  nerves  are  derived  from  the  sympathetic 
and  cerebrospinal  systems;  sympathetic  ganglion  are 
also  present. 

The  Physiological  Properties  of  Muscle  Tissue. — 
Consistency. — The  consistency  of  muscle  during  life 
depends  upon  the  activity  of  the  part  upon  which  the 
muscle  is  acting.  Relaxed  muscles  are  soft  and  fluc- 
tuating; when  touched  under  tension  or  doing  work 
the  muscles  are  hard  and  resistant.  The  degree  of 
tension  of  course  depends  upon  the  size  of  the  muscle 
and  the  amount  of  work  required. 

Cohesion. — Cohesion  of  muscle  depends  upon  the 
amount  of  connective  tissue  it  contains;  and  it  is  this 
which  enables  it  to  resist  the  forces  of  traction  and 
pressure. 

Elasticity. — Muscle  possesses  great  elasticity,  or  the 
power  to  stretch  beyond  its  normal  length  through 
the  action  of  external  forces,  and  of  resuming  the 
normal  length  when  those  forces  are  removed.  The 
degree  of  elasticity  of  muscle  during  life  depends 
upon  the  proper  amount  of  nourishment,  exercise, 
healthy  condition  of  blood,  unimpaired  nerve  supply, 
and  absence  of  any  pathologic  or  diseased  condition. 
Should  any  of  these  conditions  interfere,  the  elasticity 
would  be  impaired. 

Tonicity. — ^This  is  the  tension  or  tonus  of  the  muscle 
and  is  a .  property  which  is  essential  to  counteract 
the  stretching  of  a  muscle  and  then  to  return  and 
maintain  it  in  a  normal  state,  ready  to  be  acted  upon 
by  the  ensuing  contractions. 

Irritability  and  Contractility.  —  All  muscles  when 
irritated  by  a  stimulus  will  respond  by  a  change  of 
shape,  becoming  shorter  and  thicker — called  muscular 
contraction,  and  on  withdrawing  the  stimulus  the  muscle 
will  resume  its  normal  shape  and  position. 


122  ^  MUSCLE  TISSUE 

The  Muscle  Stimuli. — In  the  living  body  all  muscle 
tissue  contracts  in  response  to  nerve  impulses  sent 
from  the  central  nerve  system  to  the  muscles.  Experi- 
mentally and  artificially  muscles  are  stimulated  to 
contract  by  various  stimuli,  e.  g.,  mechanic — pinching, 
striking,  or  cutting  a  muscle;  chemic,  numerous  chemi- 
cal solutions;  thermic,  heated  object,  as  hot  needle  or 
wire  will  cause  a  rapid  contraction;  electric,  as  batteries 
are  used  by  physicians  as  therapeutic  agents  or  upon 
animal  tissue  during  experiments  in  the  laboratory. 

Attachments  of  Muscles. — Muscles  are  attached  to 
bones,  cartilages,  ligaments,  or  skin  by  means  of  short, 
or  long,  rounded  fibrous  cords  called  tendons,  or  by 
short,  flat,  fibrous  membranes  called  aponeuroses.  All 
muscles,  though  they  appear  to  be  attached  to  bone  or 
cartilage,  in  reality  fuse  with  the  periosteum  or  peri- 
chondrium at  the  point  of  attachment  and  do  not 
touch  the  bone  or  cartilage.  Muscles  attached  to  the 
skin  are  flat  and  thin  and  their  fibers  fuse  with  the 
areolar  tissue  just  beneath  the  skin,  as  the  muscles  of 
the  face. 

Muscles  vary  as  to  their  form.  Some  are  long,  and 
flat  or  round;  others  short,  and  flat  or  round;  still  others 
triangular  and  quadrilateral  in  shape. 

The  origin  of  a  muscle  is  called  its  head,  and  the 
portion  which  intervenes  between  the  head  and 
the  tendon  or  aponeurosis  is  termed  the  belly  or  body 
(venter) . 

Muscles  derive  their  names  from  the  part  of  the  body 
in  which  they  are  situated;  the  tibialis  anticus — the 
anterior  tibial  region,  ulnaris — ulnar  region,  radialip, 
radial  region,  etc. ;  from  the  direction  their  fibers  take 
— rectus  abdominis,  obliquus  hallucis,  trans versalis; 
according  to  their  use  or  action — ^flexors,  extensors, 
abductors,  adductors,  levators,  compressors;  from 
their  shape — deltoid,  trapezius,  digastric;  according 
to  their  number  of  divisions — biceps,   triceps;   from 


ATTACHMENTS  OF  MUSCLES  123 

their  points  of  attachment — sternohyoid,  sternomas- 
toid. 

In  describing  a  muscle  we  speak  of  its  origin  and 
insertion,  the  former  term  meaning  its  more  fixed 
point  or  central  attachment  of  the  head,  while  the 
latter  means  the  movable  point  to  which  the  force  of 
the  muscle  is  directed  and  upon  which  it  acts  when 
it  contracts.  However,  the  majority  of  muscles  act 
from  either  their  point  of  origin  or  insertion.  The 
exceptions  are  the  muscles  of  the  face,  which  arise 
from  the  bone  and  are  inserted  into  the  skin. 

It  must  be  remembered  that  no  single  muscle  can 
perform  a  movement  alone:  It  requires  several  mus- 
cles, one  set  to  fix  the  limb  or  part  called  fixation 
muscles,  and  another  to  act  upon  the  part  to  be 
flexed,  extended,  abducted,  etc. 

Tendons. — ^Tendons  when  seen  during  life  or  in  the 
recent  state  are  white,  glistening,  fibrous  cords,  of 
different  size  and  shape,  some  are  long  and  short, 
thick,  rounded,  and  flattened;  consist  mostly  of  white, 
fibrous  tissue,  very  strong  and  non-elastic.  Their 
blood-supply  is  very  scant.  The  smaller  tendons  not 
showing  a  trace  of  blood.  The  nerve  endings  have 
special  terminations  called  neurotendinous  spindles 
or  organs  of  Golgi.  The  tendons  are  attached  to  the 
belly  of  the  muscle  by  one  extremity;  to  the  periosteum 
of  bone  or  perichondrium  of  cartilage  by  the  other, 
and  are  usually  the  part  which  is  called  the  insertion. 
However,  some  muscles  have  a  tendon  at  either 
extremity,  as  the  biceps  and  triceps,  and  others  present 
two  muscular  bellies  with  a  tendon  between,  as  the 
digastric  muscle. 

Aponeuroses. — ^These  are  similar  in  structure  to 
tendons;  they  are  flat,  white,  fibrous  membranes 
attached  by  one  extremity  to  the  muscle  and  by  the 
other  to  the  bone,  cartilage,  ligament,  or  skin — as  the 
gluteus  maximus  muscle.  They  usually  are  associ- 
ated with  thin  or  thick  flat  muscles  just  beneath  the 


124  MUSCLE  TISSUE 

skin  and  fascia.  They  are  not  supplied  by  nerves,  and 
possess  a  meager  blood-supply. 

Fasciae. — When  the  skin  is  removed  the  structure 
beneath  will  appear  as  a  silvery-white  layer  through 
which  are  seen  the  muscles,  and  contained  superficial 
nerves  and  bloodvessels.  This  is  known  as  the  fascia 
which  covers  the  muscles  as  a  sheath,  also  forms 
support  and  coverings  for  the  various  organs.  It 
consists  of  layers  of  fibro-areolar  connective  tissue. 
In  certain  parts  of  the  body  the  fascia  is  found  in 
two  layers — superficial  and  deep  and  often  three,  as 
the  thigh.  Certain  muscles  are  lodged  in  the  layers 
of  fasciae,  as  the  platysma  muscle  in  the  neck,  and 
the  orbicularis  palpebrarum  muscle  around  the  eye- 
lids. The  deep  fascia  usually  forms  sheaths  for  the 
individual  muscles  of  an  extremity,  as  in  the  thigh, 
where  the  membrane  encloses  it  as  a  stocking;  this 
arrangement  increases  the  tension  and  pressure,  thus 
assisting  the  muscles  in  their  action.  In  addition  the 
deep  fascia  gives  off  septa  or  walls  which  separate 
the  muscles  of  the  limbs,  and  are  deeply  attached  to 
the  periosteum  of  the  bone;  these  are  called  intermuscu- 
lar septa.  Near  the  wrist-joint  the  deep  fascia  becomes 
thickened  and  reinforced  by  transverse  fibers  to  assist 
in  holding  in  firm  position  (front  and  back)  the  tendons 
passing  to  the  hand  and  fingers;  also  near  the  ankle- 
joint  is  a  similar  arrangement  for  the  tendons  passing 
to  the  foot  and  toes.    They  are  called  annular  ligaments. 

Description.^ — The  description  of  a  muscle  includes: 
the  location,  origin,  insertion,  relations,  action,  nerve, 
and  blood-supply. 


THE  MUSCLES  OF  THE  HEAD  AND  NECK 

The  Cranial  Region  or  Scalp. — The  scalp  consists, 
from  without  inward,  of  the  skin,  a  layer  of  adipose 

1  The  most  important  muscles  only  will  be  described. 


THE  MUSCLES  OF  THE  HEAD  AND  NECK     125 

tissue  (fat),  epicranial  aponeurosis^,  subaponeurotic 
tissue,  periosteum,  and  bone.  The  skin  is  very  thick 
and  contains  the  hair  follicles,  closely  related.  The 
superficial  fascia  beneath  the  skin  contains  fat,  super- 
ficial bloodvessels,  and  nerves  of  the  scalp;  it  is  con- 
tinuous behind  with  the  fascia  of  the  neck;  on  the  sides 
it  is  continued  over  the  temporal  fascia.  The  layers 
of  the  scalp  are  all  blended  firmly  together. 

The  Occipitofrontalis  Muscle. — ^This  is  a  broad,  thin 
layer,  consisting  of  two  muscular  portions  with  an 
intervening  aponeurosis.  The  occipital  portion  or 
occipitalis  muscles  is  attached  behind  to  the  outer 
two-thirds  of  the  upper  curved  line  on  each  side  of 
the  occipital  and  mastoid  portion  of  the  temporal 
bones.  The  frontal  portion,  or  frontalis  muscle,  arises 
from  the  aponeurosis  between  the  frontal  eminence 
of  the  frontal  bone  and  the  coronal  suture,  and  has 
no  bony  attachments. 

Actions. — ^The  frontalis  elevates  the  eyebrows,  draws 
the  scalp  forward,  and  wrinkles  the  forehead  trans- 
versely; occipitalis  draws  the  scalp  backw^ard,  or  alter- 
nates with  the  frontalis  in  moving  the  scalp  back  and 
forth — some  individuals  can  move  the  scalp  volun- 
tarily. 

The  Nerve  Supply. — Frontalis  by  temporal  branches 
of  the  facial  nerve;  occipitalis  by  the  posterior  auric- 
ular branch  of  the  facial. 


The  Muscles  to  the  External  Ear  (Auricular 
Region) 

Attrahens  aurem. 
Attollens  aurem. 
Retrahens  aurem. 

They  are  three  small  muscles  placed  just  beneath 
the  skin;  sometimes  they  are  scarcely  visible  in  man, 


126  MUSCLE  TISSUE 

consisting  of  a  few  scant  fibers.    In  mammalia  they 
are  particularly  well-developed — as  the  rabbit,  etc. 

Actions. — Is  not  marked  in  man.  Attrahens  draws 
the  ear  forward  and  upward;  attollens  raises  it  slightly; 
retrahens  draws  it  backward. 

Muscles  of  the  Eyelids  and  Eyebrows  (Palpebral 
Region) 

Orbicularis  palpebrarum 
Corrugator  supercilii 
Tensor  tarsi 

Orbicularis  Palpebrarum.— This  is  a  flat  muscle, 
consisting  of  circular  fibers  which  surround  the  cir- 
cumference of  the  orbit  and  eyelids.  Origin  from  the 
upper  and  lower  margins  of  the  internal  tarsal  liga- 
ments and  passes  out  in  a  slight  curve  across  the  upper 
lid  to  the  external  tarsal  ligament.  The  orbital  portion 
is  the  larger  and  stronger,  is  attached  to  the  nasal 
process  of  superior  maxilla,  inner  part  of  orbital  arch, 
and  externally  overlies  the  cheek  and  temple  forming 
a  series  of  concentric  loops.  The  upper  fibers  of  this 
portion  of  the  muscle  blend  with  the  fibers  of  the 
occipitofrontalis  and  corrugator  supercilii  muscles. 

The  Tarsal  Ligaments. — Internal  Tarsal  Liga- 
ment or  tendo-oculi  is  J  inch  in  length  and  about  the 
same  in  breadth.  Attached  to  the  nasal  process  of  the 
superior  maxilla  in  front  of  the  lacrymal  groove, 
then  it  passes  to  the  inner  commissure  of  the  eyelids, 
splitting  and  ending  in  the  inner  extremity  of  the 
corresponding  tarsal  plate  of  the  eyelids;  crossing  the 
lacrymal  sac  the  tendon  gives  off  a  strong  aponeurotic 
layer  from  its  posterior  surface,  which  spreads  over 
the  sac,  and  is  attached  to  the  ridge  on  the  lacrymal 
bone — this  latter  is  the  reflected  aponeurosis  of  the 
tendo  oculi.  The  external  tarsal  ligament  is  weaker 
than  the  former  and  arises  from  the  frontal  process 


THE  MUSCLES  OF  THE  HEAD  AND  NECK     127 

of  the  malar  bone  to  be  inserted  into  each  tarsal  plate 
at  the  external  commissure  of  the  eyelids. 

Actions. — Orbicularis  palpebrarum  is  the  muscle 
which  closes  the  eye  suddenly,  as  in  winking,  or  as  a 
protection  in  shutting  the  eye  against  the  entrance 
of  a  foreign  body.  The  palpebral  portion  closes  the 
lids,  as  in  sleep.  The  tendo-oculi  serves  to  suck  the 
tears  into  the  lacrymal  sac,  by  its  attachment  to  the 
sac.     (See  Lacrymal  Apparatus,  page  398). 

Nerve  Supply — facial  nerve. 

Corrugator  Supercilii. — ^They  are  two  small  muscles 
found  at  the  inner  extremity  of  the  eyebrow,  beneath 
the  occipitofrontalis  and  orbicularis  palpebrarum,  with 
which  they  fuse. 

Action  is  to  draw  the  eyebrow  downward  and  inward 
and  to  form  the  vertical  wrinkles  of  the  forehead;  it 
is  called  the  "frowning"  muscle,  and  is  the  means  of 
expressing  anxiety,  suffering,  and  thought. 

Nerve  Supply — facial  nerve. 


The  Muscles  of  the  Orbit  (Orbital  Region) 

Levator  palpebrse  superioris     Rectus  internus 
Rectus  superior  Rectus  externus 

Rectus  inferior  Obliquus  oculi  superior 

Obliquus  oculi  inferior 

Levator  Palpebrse  Superioris. — This,  the  elevator  of 
the  upper  lid,  is  a  thin,  flat,  and  slightly  triangular- 
shaped  muscle  found  within  the  orbital  cavity  (and 
like  the  other  muscles  of  this  group  cannot  be  seen 
until  the  skull-cap  has  been  removed  and  the  roof  of 
the  orbit  opened)  above  the  eye-ball. 

Actions. — Raises  the  upper  eyelid  and  is  the  opposite 
in  action  to  the  palpebral  portion  of  the  orbicularis 
palpebrarum. 

Nerve  Supply. — ^IMotor  oculi  or  third  cranial  nerve. 


128 


MUSCLE  TISSUE 


The  Four  Recti  Muscles. — They  arise  from  a  common 
fibrous  membrane  attached  at  the  apex  of  the  orbital 
cavity,  above,  below,  and  internal  to  the  margins  of 
the  optic  foramen  and  fuse  with  the  optic  nerve. 
They  all  pass  obliquely  forward  and  are  inserted 
into  the  superior,  inferior,  internal,  and  external  por- 
tions of  the  eye-ball  (in  the  position  implied  by  their 
names)    by    a    tendinous    expansion   into    the    sclera 


(outer  coat  of  eye-ball)  about 
cornea. 

Fig.  63 


of  an  inch  from  the 


Muscles  of  the  right  orbit.     (Gray.) 


Actions. — The  four  recti  are  so  attached  that  they 
are  able  to  turn  the  eye-ball  in  the  direction  desired, 
expressed  by  their  names — thus  upward,  downward, 
inward,  or  outward.  The  obliquus  ocuH  superior  and 
inferior  assist  the  superior  and  inferior  recti  to  turn  the 
eye-ball  downward,  inward,  or  outward,  and  upward, 
outward,  or  inward.  The  internal  and  external  recti 
also  assist  in  these  complicated  actions  of  the  eyes. 


THE  MUSCLES  OF  THE  HEAD  AND  NECK     129 

Nerve  Supply. — ^All  supplied  by  the  motor  oculi  or 
third  cranial  nerve,  except  the  external  rectus,  and  it 
is  innervated  by  the  abducent  or  sixth  cranial  nerve; 
the  superior  oblique  is  supplied  by  the  trochlear  or 
fourth  cranial  nerve. 

The  Muscles  of  the  Nose  (Nasal  Region) 

Pyramidalis  nasi.  Dilator  naris  anterior. 

Levator  labii  superioris  Compressor  nasi. 

alseque  nasi.  Compressor  narium  minor. 

Dilator  naris  posterior.  Depressor  alse  nasi. 

The  above  muscles  are  just  beneath  the  skin  and 
fascia  and  most  of  them  are  inserted  into  the  skin; 
they  arise  from  the  bones,  fascia,  and  cartilages. 

The  Muscles  of  the  Cheeks  and  Lips  (Maxillary 
Region) 

Levator  labii  superioris.         Zygomaticus  major. 
Levator  anguli  oris.  Zygomaticus  minor. 

The  Levator  Labii  Superioris. — Origin,  lower  margin 
of  orbit,  some  fibers  from  maxilla  and  malar  bones, 
insertion  into  muscular  portion  of  upper  lip.  Action 
— elevates  and  assists  in  protruding  the  upper  lip. 
Nerve,  facial. 

The  Levator  Anguli  Oris. — Origin,  canine  fossa  of 
maxilla;  inserted  into  skin  and  fascia  near  angle  of 
mouth,  blending  with  the  fibers  of  the  zygomaticus 
major,  depressor  anguli  oris,  and  orbicularis  oris. 
Action — elevates  angle  of  mouth.    Nerve,  facial. 

Zygomaticus  Major. — Origin,  malar  bone;  inserted 
into  skin  and  fascia  outer  portion  of  upper  lip  and  angle 
of  mouth,  blending  with  the  fibers  of  the  levator 
anguli  oris,  orbicularis  oris,  and  the  depressor  anguli 
oris.  Action — draws  the  angle  of  the  mouth  upward 
and  backward,  as  in  laughing.  Nerve,  facial. 
9 


130  MUSCLE  TISSUE 

Zygomaticus  Minor. — Origin,  malar  bone;  inserted 
into  skin  and  fascia  of  upper  lip  internal  to  angle  of 
mouth  and  the  insertion  of  the  zygomaticus  major; 
fuses  with  jSbers  of  orbicularis  oris.  Action — draws  the 
upper  lip  backward,  upward,  and  outward,  thus  gives 
to  the  face  an  expression  of  sadness.    Nerve,  facial. 

The  Muscles  of  the  Chin  and  Lower  Lip  (Mandibular 
Region) 

Levator  menti. 
Depressor  anguli  oris. 
Depressor  labii  inferioris. 

Levator  Menti. — Origin,  mandible  external  to  sym- 
physis; inserted  into  skin  of  chin.  Action — ^raises  lower 
lip,  wrinkles  chin,  gives  to  the  face  the  expression  of 
doubt,  disdain,  and  pouting.    Nerve,  facial. 

Depressor  Anguli  Oris. — Origin,  from  mandible,  in- 
serted into  angle  of  mouth.  It  is  blended  with  the 
platysma,  orbicularis  oris,  risorius,  and  levator  anguli 
oris.  Action — depresses  angle  of  mouth.  Acting  with 
the  levator  anguli  oris  the  two  will  depress  angles  of 
the  mouth  directly  inward,  as  in  smirking.  Nerve, 
facial. 

Depressor  Labii  Inferioris. — Origin  from  mandible; 
insertion,  skin  of  lower  lip,  blends  with  fibers  of  orbicu- 
laris oris  and  muscle  of  opposite  side.  Action  depresses 
lower  lip.    Nerve,  facial. 

The  Muscles  of  the  Buccal  Region 

Orbicularis  oris. 

Buccinator. 

Risorius. 

Orbicularis  Oris. — This  is  the  muscle  of  the  mouth 
and  lips.    It  consists  of  oblique  and  transverse  fibers 


THE  MUSCLES  OF  THE  HEAD  AND  NECK     131 

which  are  not  distinct,  but  fuse  with  the  muscles  in- 
serted into  the  skin  and  mucous  membrane  surround- 
ing the  mouth.  The  buccinator  muscle  divides  at  the 
angle,  and  the  fibers  pass  into  the  upper  and  lower 
part  of  the  orbicularis  oris;  also  at  the  angle  entering 
from  above  are  the  fibers  of  the  levator  anguli  oris, 
and  from  below  the  fibers  of  the  depressor  anguli  oris. 
In  addition  to  the  former  muscles  crossing  at  the  angle, 
are  the  fibers  of  the  risorius  which  divide  and  blend 
with  the  upper  and  lower  lips  respectively.  The  other 
muscles  inserted  into  the  lips  are:  above,  levator  labii 
superioris  (elevator  of  upper  lip);  levator  labii  supe- 
riors alaeque  nasi  (elevator  of  the  upper  lip  and  wing 
of  the  nose);  the  zygomaticus  major  and  minor;  and 
depressor  labii  inferioris  (depressor  of  the  lower  lip). 
Actions  are  numerous  and  various,  and  only  the  ordi- 
nary or  chief  actions  will  be  mentioned,  as  the  muscles 
inserted  into  the  orbicularis  oris  all  aid  it  in  the  com- 
plex movements  of  this  important  muscle  of  expression. 
When  the  fibers  contract  they  close  the  lips;  the  crossed 
fibers  consisting  of  the  superficial  set  brings  the  lips 
together  and  also  protrudes  them  as  in  whistling, 
pouting,  etc.,  the  deep  fibers  assisted  by  the  oblique 
fibers  forcibly  close  the  lips  and  hold  them  against  the 
teeth — as  when  one  refuses  to  take  food  or  medicine 
by  mouth. 

Nerve — facial. 

Buccinator. — This  is  the  chief  muscle  of  the  cheek, 
and  encloses  the  space  between  the  two  jaw  bones. 
It  is  thus  quadrilateral  in  shape.  Arises  from  the  alve- 
olar processes  of  the  maxillag  and  mandible,  behind  from 
a  thickened  fibrous  band,  called  the  pterygomandibular 
ligament.  The  fibers  come  together  at  the  angle  of  the 
mouth  and  pass  to  the  upper  and  lower  lips.  Action — 
it  is  essentially  a  muscle  of  mastication.  The  muscle 
contracts  the  cheeks  and  compresses  them  so  that  the 
food  during  mastication  is  kept  within  the  bounds  of 
the  teeth  and  comes  in  contact  with  their  chewing 


132  MUSCLE  TISSUE 

or  grinding  action.  When  the  cheeks  are  distended 
with  air,  the  muscle  contracts  and  expels  it  through  the 
lips  as  in  playing  the  cornet,  flute,  etc. 

Nerve — facial. 

Risorius. — A  small  thin  muscle  arises  from  the  fascia 
over  the  masseter  muscle,  inserted  into  muscular  and 
subcutaneous  tissue  at  the  angle  of  the  mouth. 

Action. — Draws  back  the  angle  of  the  mouth  as  seen 
in  lockjaw,  giving  the  peculiar  expression  to  the  face 
known  as  the  "sardonic  grin  or  laugh;"  also  (both 
sides)  assists  in  retracting  angles  of  mouth  as  in 
smiling,  associated  with  the  other  muscles  at  the 
angle. 

Nerve — facial. 

Muscles  of  Mastication 

Temporomandibular  region.  Pterygomandibular  region. 
Masseter.  External  Pterygoid. 

Temporal.  Internal  Pterygoid. 

The  muscles  of  mastication  aid  in  preparing  the  food 
so  that  it  can  be  easily  swallowed.  They  bring  the 
jaws  together,  so  that  the  teeth  approximate  and  chew, 
or  by  a  lateral  motion,  grind  the  food. 

The  Muscles  of  the  Tongue  (Lingual  Region) 

The  muscles  of  the  tongue  are  divided  into  extrinsic, 
those  situated  outside  of  the  organ,  yet  are  inserted 
into  it;  and  intrinsic,  those  contained  within  the  organ, 
forming  its  substance. 

The  Extrinsic  Muscles. — ^These  are:  geniohyoglossus, 
hyoglossus,  styloglossus,  palatoglossus,  and  chondroglossus. 

The  Intrinsic  Muscles. — ^These  are  a  series  of  inter- 
lacing fibers  making  up  the  substance  of  the  tongue 
and  are  named  according  to  their  position  and  direc- 
tion,   called   lingualis,   presenting — superior,    inferior. 


THE  MUSCLES  OF  THE  HEAD  AND  NECK     133 

transverse,  and  vertical  fibers,  with  a  medium  fibrous 
septum.  They  all  receive  fibers  from  the  extrinsic 
muscles  at  their  points  of  insertion  into  the  tongue. 

The  Muscles  of  the  Soft  Palate  (Palatal  Region) 

The  soft  palate  is  continued  back  from  the  hard 
palate,  and  is  seen  on  opening  the  mouth  as  an  arch 
with  a  central  projection  called  the  uvula,  directly 
over  the  back  of  the  tongue.  Beneath  the  mucous 
membrane  covering  these  parts  are  the  muscles  of  the 
soft  palate,  as  follows: 

Levator  palati.  Palatoglossus. 

Tensor  palati.  Palatopharyngeus. 

Azygos  uvulse.  Salpingopharyngeus. 

The  Muscles  of  the  Pharynx  (Pharyngeal  Region) 

Superior  constrictor.       Inferior  constrictor. 
Middle  constrictor.         Stylopharyngeus. 

These  muscles  are  divided  into  two  layers — an 
outer  flat  and  thin  one — called  the  constrictors,  with  a 
transverse  set  of  fibers;  an  inner — called  the  elevators, 
two  in  number,  with  a  longitudinal  arrangement  of 
the  fibers. 

Actions  of  pharyngeal  muscles.  Their  chief  function 
is  to  assist  in  swallowing  the  food  after  it  has  been 
masticated  and  forced  into  the  pharynx  by  the  tongue 
and  muscles  of  the  soft  palate.  At  the  beginning  of 
deglutition  the  sides  of  the  pharynx  are  raised  upward 
and  outward  by  the  two  stylopharyngei  muscles, 
at  the  same  time  the  larynx  and  tongue  are  carried 
forward.  When  the  bolus  of  food  is  being  received 
into  the  pharynx,  the  elevator  muscles  relax  and  the 


134 


MUSCLE  TISSUE 


constrictor  muscles  contract  upon  the  mass  and  force 
it  into  the  esophagus. 


Fia.  64 


Muscles  of  the  pharynx.     External  view.     (Gray.) 

The  Muscles  and  Fasciae  of  the  Neck 

The  neck  muscles  are  divided  into  a  superficial  and 
a  deep  set.  They  are  arranged  vertically  and  only  the 
anterior  or  superficial  set  will  be  described,  as  the  others 
are  not  important  so  far  as  the  nurse^s  knowledge  is 
concerned. 


THE  MUSCLES  OF  THE  HEAD  AND  NECK     135 

The  Anterior  Neck  Muscles. — The  platysma  is  a  thin, 
pale  muscle,  extending  over  the  front  and  sides  of  the 
neck,  the  lower  region  of  the  face,  and  as  low  as  the 

Fia.  65 


Muscles  of  the  neck  and  boundaries  of  the  triangles.     (Gray.) 

upper  aspect  of  the  chest,  just  below  the  clavicles.  It 
is  just  beneath  the  skin,  invested  by  the  superficial 
fascia,  and  above  the  deep  cervical  fascia  of  the  neck. 
There  are  two  such  muscles. 


136  MUSCLE  TISSUE 

The  Steraomastoid. — Origin,  from  anterior  surface  of 
the  sternum,  inner  third  of  upper  surface  of  clavicle; 
two  portions  meet  and  pass  obliquely  upward  and 
back  across  the  lateral  aspect  of  the  neck  to  be  inserted 
into  the  anterior  border  and  outer  surface  of  the 
mastoid  portion  of  the  temporal  bone. 

Actions. — ^The  two  muscles  acting  together  bend  the 
head  upon  the  neck.  When  only  one  muscle  contracts 
the  head  is  drawn  toward  the  shoulder  of  the  same 
side,  at  the  same  time  the  head  is  rotated,  so  that  the 
face  is  carried  to  the  opposite  side.  When  the  head 
is  held  firm  by  the  other  muscles  the  sternomastoid 
acts  as  a  muscle  of  respiration  in  forced  breathing. 
Nerve — spinal  accessory  and  deep  branches  of  cervical 
plexus. 

Depressors  of  the  Hyoid  Bone 

Sternohyoid .  Thyrohyoid . 

Sternothyroid.  Omohyoid. 

The  Elevators  of  the  Hyoid  Bone 

These  muscles  are  situated  at  the  inferior  and  lateral 
aspect  of  the  floor  of  the  mouth,  below  the  mandible. 
They  are  covered  by  the  deep  cervical  fascia  of  the 
neck. 

Digastric.  Mylohyoid. 

Stylohyoid.  Geniohyoid. 

Deep  Neck  Muscles 

There  are  numerous  neck  muscles  deeply  located  in 
the  neck;  they  assist  to  maintain  the  head  erect  and 
also  aid  in  flexing,  extending,  and  rotating  the  head  on 
the  spinal  column.  A  description  of  these  muscles  will 
not  be  given,  as  they  cannot  be  properly  understood 


THE  MUSCLES  AND  FASCIA  OF  THE  TRUNK     137 

unless  seen,  either  in  a  diagram,  or  the  human  body. 
Other  muscles  arising  froni  the  cervical  vertebrae  pass 
to  the  ribs  and  aid  in  forced  inspiration  and  expiration ; 
still  others  posteriorly  pass  to  the  scapulae  and  thoracic 
vertebrae  and  assist  in  shrugging  the  shoulders,  flexing 
and  extending  spinal  column,  rotating  the  vertebrae,  etc. 


THE  MUSCLES  AND  FASCIiE  OF  THE  TRUNK 

In  speaking  of  the  trunk  we  include  that  part  of  the 
human  body  consisting  of  the  back,  thorax,  abdomen, 
and  perineal  region. 


The  Muscles  of  the  Neck  and  Back 

The  muscles  of  these  regions  are  in  layers,  their 
actions  and  relations  are  too  complex  to  include  here 
except  the  ones  described  below.  It  is  suflScient  to 
state  that  they  consist  of  five  layers,  in  which  are 
thirty-two  or  more  pairs  of  muscles.  These  muscles 
are  covered  by  a  superficial  fascia  which  is  continuous 
with  the  fascia  over  the  rest  of  the  body;  and  a  deep 
fascia,  which  is  thick  and  fibrous,  and  curves  over  and 
forms  sheaths  for  the  muscles,  being  attached  to  the 
following  bony  prominences:  occipital  bone,  crest  of 
ilium,  spines  of  vertebrae,  and  the  spines  of  the  scap- 
ulae. In  the  neck  it  forms  the  posterior  portion  of  the 
deep  cervical  fascia,  in  the  thorax  blends  with  the 
axillary  fascia  and  deep  fascia  of  the  thorax;  it  is 
continuous  with  the  abdominal  fascia,  also  forms  the 
back  layer  of  the  lumbar  fascia,  and  covers  the  erector 
spinae  mass  of  muscles. 

The  Trapezius. — This  is  the  muscle  situated  at  the 
back  of  the  neck  and  shoulders.  There  are  two.  Origin, 
inner  third  of  the  superior  curved  line  of  the  occipital 
bone,  ligamentum  nuchae,  spinous  processes  of  the 
seventh  cervical  and  all  the  thoracic  vertebrae  and 


138 


MUSCLE  TISSUE 


supraspinous  ligaments;  insertion,  fibers  converge  to 
shoulder  girdle;  superior  ones  to  outer  third  or  half 


Muscles  in  the  second  layer  of  the  back  and  on  the  dorsum  of  the  shoulder. 

(Testut.) 


THE  MUSCLES  AND  FASCIA  OF  THE  TRUNK     139 

of  the  posterior  border  of  the  clavicle  (collar  bone); 
middle  fibers  horizontally  to  inner  margin  of  acromion 
and  superior  lip  of  spine  of  scapula;  inferior  fibers 
terminate  in  a  triangular  aponeurosis,  which  glides 
over  a  smooth  surface  at  the  inner  extremity  of  the 
spine  to  be  inserted  into  a  tubercle  at  the  outer  portion 
of  this  surface. 

Latissimus  Dorsi.^This  is  one  of  the  largest  and 
longest  muscles  in  the  body.  Broad  and  flat  at  its 
origin,  narrow  at  its  insertion,  it  covers  the  lumbar 
region  of  the  back  and  the  lower  half  of  the  thoracic 
region.  Origin,  spinous  processes  of  the  lower  six 
or  seven  thoracic  vertebrae,  posterior  layer  of  lumbar 
aponeurosis  which  attaches  it  to  the  lumbar  and  sacral 
spines,  and  supraspinous  ligament,  from  the  outer  lip 
of  the  iliac  crest,  also  arises  by  three  or  four  fleshy  slips 
from  three  or  four  lower  ribs.  Its  upper  fibers  pass 
horizontally  outward,  the  middle  obliquely  upward, 
and  the  lower  fibers  vertically  upward,  they  become 
narrowed  into  a  tendon,  IJ  inches  wide,  which  passes 
back  of  the  arm-pit  (axilla)  in  front  of  the  teres  major 
muscle,  to  be  inserted  into  the  bicipital  groove  on  the 
anterior  and  upper  aspect  of  the  humerus  (arm 
bone). 

Actions. — Depresses  arm;  draws  it  toward  body 
(adducts);  turns  it  inward;  acts  in  striking  a  blow 
or  chopping  wood,  etc.;  when  arms  are  firmly  held 
in  position,  it  assists  the  chest  and  abdominal  muscles 
to  suspend  and  draw  forward  or  upward  the  whole 
trunk,  as  in  climbing,  etc.  Nerve — subscapular  from 
brachial  plexus. 


The  Muscles  of  the  Thorax 

External  intercostals.  Triangularis  sterni. 

Internal  intercostals.  Levatores  costarum. 

Infracostales  (subcostales) .  Diaphragm. 


140  MUSCLE  TISSUE 

The  Intercostal  Muscles. — These  are  thin,  flattened 
muscles  extending  between  the  margins  of  two  adjacent 
ribs,  fining  the  intervening  spaces — called  intercostal. 
These  muscles  are  covered  by  the  intercostal  fascia, 
internally  and  externally,  and  a  layer  lies  between 
the  two  muscles. 

The  Subcostals. — ^The  subcostals  (infracostals)  or 
muscles  below  the  lower  ribs  consist  of  muscular  and 
aponeurotic  fibers,  which  are  attached  to  the  inner 
surface  of  one  rib  (usually  lower  ribs),  and  inserted 
into  the  inner  surfaces  of  the  first,  second,  or  third  rib 
below.  They  are  placed  on  the  parts  of  the  ribs 
where  the  internal  intercostal  muscles  end  posteriorly. 

The  Triangularis  Stemi. — ^This  is  a  thin,  irregular- 
shaped  muscle  found  on  the  posterior  surface  of  the 
sternum  (breast  bone),  and  it  passes  to  the  costal 
cartilages  of  the  ribs  from  the  second  to  sixth  inclusive. 
It  is  a  single  muscle. 

The  Levatores  Costarum  (Elevators  of  the  Ribs). — ^These 
are  twelve  in  number  found  on  each  side  of  the  verte- 
bral column  external  to  the  thoracic  cavity.  Origin, 
by  small  tendinous  and  fleshy  bundles  from  the  ex- 
tremities of  the  transverse  processes  of  the  seventh 
cervical  and  the  eleven  upper  thoracic  vertebrae;  pass 
obliquely  downward  and  outward  to  be  inserted  into 
the  upper  border,  between  the  angle  and  tubercle  of 
the  rib,  immediately  below^  its  vertebra  of  origin. 
Each  of  the  lower  elevator  muscles  divides  into  two 
slips,  one  of  which  is  inserted  as  described  above 
the  other  slip  passes  to  the  second  rib  below  its  origin; 
thus  each  of  the  lower  ribs  receives  fibers  from  two 
vertebrae. 

Diaphragm. — ^This  is  a  musculofibrous  wall  which 
divides  the  thoracic  and  abdominal  cavities.  It  is 
dome-shaped;  the  convex,  upper  surface  forms  the 
floor  of  the  thoracic  cavity,  and  the  concave  lower 
surface  the  roof  of  the  abdominal  cavity.  The  attach- 
ments of  the  diaphragm  are  as  follows :    In  front  the 


THE  MUSCLES  AND  FASCIJH  OF  THE  TRUNK     141 

lower  six  cartilages — internal  surface,  back  of  ensi- 
form;  behind — from  the  lumbar  vertebrae  by  two  slips 
or  crura;  and  from  aponeurotic  arches — the  arcuate 
ligaments.  The  crura  are  found  on  the  bodies  of  the 
lumbar  vertebrae,  on  each  side  of  the  aorta.  The 
internal  arcuate  ligament  passes  over  the  psoas  muscle 
from  the  outer  side  of  the  body  of  the  first  lumbar 
vertebra  to  the  lip  of  the  transverse  process.     The 

Fig.  67 


I'J'i  ..\  iifjJiS 


Diaphragm,  viewed  from  in  front.     (Testut.) 

external  arcuate  ligament  passes  over  the  quadratus 
lumborum  from  the  second  transverse  process  to  the 
tip  of  the  last  rib.  The  fibers  of  the  diaphragm  arise 
from  these  ligaments.  The  muscular  fibers  on  reaching 
the  centre  became  fibrous,  and  form  the  central  tendon 
of  the  diaphragm.  The  fibers  are  interwoven  in  every 
direction.  The  pericardium  (the  serous  membrane 
covering  the  heart)  is  attached  to  the  upper  surface 
of  this  central  tendon. 


142  MUSCLE  TISSUE 

There  are  three  important  openings  in  the  dia- 
phragm, and  several  smaller  ones.  The  esophageal 
opening  transmits  the  esophagus  and  vagi  nerves,  the 
esophagus  continues  as  the  stomach  below  the  dia- 
phragm; the  aortic  opening  transmits  the  abdominal 
aorta,  vena  azygos  major,  and  thoracic  duct;  it  is  the 
most  posterior  one;  the  opening  for  the  inferior  vena 
cava  is  the  most  anterior  and  transmits  the  large  vein 
which  carries  the  venous  blood  to  the  right  side  of 
the  heart.  The  splanchnic  nerves  and  the  azygos 
minor  veins  pierce  the  diaphragm  near  the  crura.  The 
upper  surface  of  the  diaphragm  is  covered  by  peri- 
cardium in  the  centre,  pleurae  on  the  lateral  surfaces, 
and  the  under  surface  is  covered  by  peritoneum. 

Actions. — It  is  the  chief  muscle  of  respiration; 
thus  when  a  deep  breath  is  taken  the  diaphragm  can 
be  felt  to  extend  downward  making  pressure  on  the 
abdominal  organs,  and  at  the  same  time  increases 
the  vertical  diameter  of  the  thoracic  cavity,  allowing 
the  lungs  to  fill  more  readily  with  air.  The  diaphragm 
also  contracts  in  all  expulsive  acts,  as  sneezing,  laugh- 
ing, crying,  coughing,  and  in  the  act  of  defecation, 
urination,  and  expulsion  of  the  fetus  during  delivery, 
it  assists  the  abdominal  muscle  to  raise  the  intra- 
abdominal pressure.  The  action  of  the  diaphragm  can 
be  seen  in  patients  under  ether,  when  the  upper  por- 
tion of  the  abdomen  will  demonstrate  the  gradual 
and  steady  ascent  and  descent  of  the  diaphragm 
under  forced  or  abdominal  breathing. 


The  Fasciae  and  Muscles  of  the  Abdomen 

The  fascia  of  the  abdomen  is  divided  into  a  super- 
ficial and  deep  portion.  The  superficial  fascia  is 
continuous  above  with  the  fascia  of  the  thorax  and 
back,  below  with  that  of  the  thigh.  Its  lower  fourth 
on   the    abdomen   divides   into  a  superficial  layer  — 


THE  MUSCLES  AND  FASCIA  OF  THE  TRUNK     143 

called  Camper's  fascia,  and  a  deep  layer  —  termed 
Scarpa's. 

The  deep  layer  is  attached  to  Poupart's  ligament, 
and  is  continued  around  the  male  and  female  genitalia; 
the  superficial  layer  also  passes  to  the  male  and  female 
genitalia.  The  deep  fascia  of  the  abdomen  is  so 
adherent  to  the  underlying  structures  that  it  is  difficult 
to  see. 

The  Muscles  of  the  Abdomen. — ^They  are  as  follows: 

External  oblique.  Trans versalis. 

Internal  oblique.  Rectus. 

Pyramidalis. 

The  external  and  internal  oblique  and  the  trans- 
versahs  are  thin,  flat,  broad  muscles  which  possess 
aponeuroses  and  they  all  form  with  the  rectus  the 
anterior  and  lateral  abdominal  walls,  being  lined — the 
transversalis — by  the  peritoneum.  They  are  arranged 
one  on  either  side.  The  aponeuroses  of  the  oblique 
and  transversalis  pass  toward  the  outer  edge  of  the 
rectus  and  ensheath  the  two  halves.  In  a  general  way 
the  oblique  and  transversalis  muscles  are  attached  to  the 
lower  ribs,  crest  of  the  ilium,  and  Poupart's  ligament. 

The  Fasciae  and  Muscles  of  the  Thofacic  Region, 
Fascia,  of  Pectoral  Region  (Chest). — Superficial  contains 
the  mammary  gland,  sending  septa  into  it  and  support- 
ing it.  The  deep  fascia  is  thin,  covering  the  surface 
of  the  pectoralis  major  muscle;  it  is  attached  to  the 
middle  of  the  front  of  the  sternum,  above  to  the 
clavicle,  and  below  is  continuous  with  the  fascia  over 
the  shoulder,  axilla,  and  thorax.  It  encloses  the  space 
between  the  pectoralis  major  and  latissimus  dorsi 
muscles;  it  is  called  in  this  region  the  axillary  fascia. 

The  Muscles  of  the  Anterior  Thora^cic  Region. 
These  are  as  follows: 

Pectoralis  major.  Subclavius. 

Pectoralis  minor. 


144  MUSCLE  TISSUE 

Pedoralis  Major. — ^This  arises  from  the  inner  half 
of  the  anterior  surface  of  the  clavicle,  the  sternum, 
from  the  upper  six  rib  cartilages  and  from  the  anterior 
sheath  of  the  rectus  and  external  oblique  aponeurosis. 
The  fibers  converge  to  be  inserted  by  two  tendons, 
united  along  the  lower  margin,  into  the  external 
bicipital  ridge  of  the  humerus. 

Subclavius. — This  arises  from  the  groove  on  the  under 
surface  of  the  clavicle  and  recess  between  the  conoid 
and  trapezoid  ligaments:  inserted  into  the  junction 
of  the  first  rib  with  its  cartilage  between  the  fibers 
of  the  costoclavicular  ligament. 

Pedoralis  Minor. — ^This  arises  from  three  ribs  near 
their  cartilages,  usually  the  third,  fourth,  and  fifth, 
often  the  second,  third,  and  fourth  or  fifth,  and  from 
the  intercostal  aponeurosis;  insertion,  inner  border  and 
upper  surface  of  the  coracoid  process  of  the  scapula; 
a  bursa  is  under  its  insertion. 

The  linea  alba  is  a  narrow  depression  seen  along  the 
middle  line  of  the  abdomen,  extending  from  the  tip  of 
the  breast  bone — ensiform — to  the  symphysis  pubes. 
It  is  formed  by  the  union  of  the  aponeuroses  of  the 
oblique  and  transversalis  muscles,  which  surround  the 
recti  muscles  and  adhere  to  the  fascia  and  skin.  A 
little  below  the  midpoint  of  the  hnea  alba  is  a  scar — 
the  result  of  the  healed  umbilical  cord,  called  the 
umbilicus    (navel). 

The  linea  semilunaris  is  a  depression  seen  on  the  outer 
side  of  each  rectus  abdominis  muscle,  and  corresponds 
to  the  line  of  fusion  of  the  aponeuroses  of  the  oblique 
and  transversalis  muscles,  as  they  blend  to  pass  in 
front  and  behind  the  recti  muscles  to  form  the  sheath 
of  the  latter  muscles.  It  extends  from  opposite  the 
ninth  costal  cartilage  to  the  spine  of  the  pubic  bone. 

Linese  transversse  are  depressions  seen  along  the  recti 
muscles,  and  correspond  to  the  attachment  of  the 
aponeuroses  of  the  abdominal  muscles  to  the  rectus. 
They  are  usually  three — one  below  the  ensiform  car- 


THE  MUSCLES  AND  FASCIA  OF  THE  TRUNK     145 

tilage,  one  between  the  ensiform  and  the  umbilicus, 
and  one  opposite  or  below  the  umbilicus. 

Actions  of  the  Abdominal  Muscles. — When  the  thorax 
and  pelvis  are  fixed  these  muscles  acting  together 
a)nstrict  the  abdominal  cavity,  and  raising  the  intra- 
abdominal pressure — also  assisted  by  the  diaphragm 
— aid  in  expelling  the  fetus  from  the  uterus,  feces  from 
the  rectum,  urine  from  the  bladder. 

The  Posterior  Muscles  of  Abdomen  (Hiac  Region) 

The  iliac  fascia  covers  the  iliopsoas  muscle,  within 
the  back  part  of  the  abdominal  cavity  stretched  from 
the  iliac  crest  to  the  iliac  portion  of  the  iliopectineal 
line.  Below  it  passes  beneath  the  femoral  vessels, 
forming  the  hinder  part  of  the  femoral  sheath;  outside 
the  vessels  it  unites  with  the  transversalis  fascia  at 
Poupart's  ligament. 

Quadratus  Lumbonim. — A  quadrilateral  muscle 
placed  between  the  last  rib  and  the  pelvis.  Origin, 
iliolumbar  ligament,  external  lip  of  the  crest  of  the 
ilium  for  two  inches,  from  two,  three,  or  four  lumbar 
transverse  processes  by  fleshy  slips  passing  up  ante- 
riorly; insertion,  inner  half  of  last  rib  and  upper  four 
lumbar  transverse  processes. 

Nerves. — Last  dorsal  and  upper  lumbar. 

Actions. — ^Lateral  flexion  of  both  may  extend  the 
spine.  Draws  down  the  last  rib,  giving  fixed  point 
for  the  diaphragm,  and  aids  inspiration.  Fixed  above, 
draws  pelvis  to  one  side,  or  both  draw  it  forward. 

Iliopsoas. — It  has  a  broad  outer  head,  iliacus,  and 
a  narrow  inner  head,  psoas  magnus. 

Iliacus. — Origin,  upper  half  of  the  iliac  fossa  down 
as  far  as  the  anterior  inferior  spine,  posteriorly  from 
ala  of  the  sacroiliac  and  iliolumbar  ligaments.  In- 
serted mostly  into  tendon  of  the  psoas;  outermost 
fibers  pass  to  the  femur  in  front  of  and  below  the  small 
trochanter. 
10 


146  MUSCLE  TISSUE 

Psoas  Magnus  {or  Major). — Origin,  by  &Ye  fleshy 
slips  from  anterior  surfaces  and  lower  borders  of  the 
lumbar  transverse  process,  and  by  a  series  of  processes, 
each  from  a  disk  and  contiguous  margins  of  two  bodies; 
the  highest  is  attached  to  the  last  thoracic  and  first 
lumbar,  and  lowest  to  the  fourth  and  fifth  lumbar 
and  intervertebral  substance  between  them;  fibers 
also  come  from  the  sacroiliac  joint  and  sacrum.  These 
attachments  are  connected  with  arches  passing  over 
the  middle  of  the  vertebrae.  The  fibers  all  unite  to  a 
thick,  long  muscle  running  along  the  brim  of  the 
pelvis,  passing  under  Poupart's  ligament,  and  inserted 
by  a  tendon  into  the  small  trochanter;  separated  by 
a  bursa. 

The  common  tendon  is  also  separated  from  the  cap- 
sule of  the  hip  by  a  bursa. 

Psoas  Parvus  (or  Minor). — Placed  on  the  surface 
of  the  psoas  magnus;  rises  from  the  bodies  of  the  last 
thoracic  and  first  lumbar  vertebrse  and  disk  between; 
ends  in  a  flat  tendon  merged  into  the  iliac  fascia  and 
inserted  into  the  iliopectineal  line  and  eminence. 
When  present  its  origin  is  variable;  was  absent  on 
both  sides  in  40  per  cent,  of  cases. 

The  Muscles  and  Fasciae  of  the  Perineum 

These  are  the  structures  which  enclose  the  space 
between  the  rami  of  the  pubes  and  ischii  on  both 
sides  and  the  pubic  arch  and  subpubic  ligament  in 
front,  while  they  are  bounded  behind  by  a  line  extend- 
ing transversely  between  the  anterior  edge  of  the 
tuberosities  of  the  ischii  on  both  sides.  The  space 
in  front  of  this  line  is  termed  the  perineum,  and  behind 
the  line,  the  space  in  front  of  the  coccyx,  is  called  the 
ischiorectal  region;  this  space  is  bounded  on  the  sides 
by  the  gluteus  maximus  muscles. 

The  perineum  can  be  demonstrated  only  by  having 
the  subject  on  its  back  with  the  limbs  flexed  on  the 


MUSCLES  AND  FASCIA  OF  UPPER  EXTREMITY  147 

abdomen.  The  structures  to  be  seen  are  the  anus 
(outlet  of  rectum),  the  scrotum  in  the  male,  and  the 
vagina  in  the  female. 

The  perineum  is  covered  by  skin,  superficial  fascia 
divisible  into  a  superficial  layer,  and  a  deep  layer — 
called  Colics'. 

The  deep  perineal  or  subpubic  fascia  or  triangular 
ligament  of  the  urethra  is  stretched  across  the  subpubic 
arch  and  consists  of  two  layers;  the  inferior  layer 
extends  back  to  the  central  point  of  the  perineum, 
attached  to  the  ischiopubic  rami,  connected  at  its 
base  with  the  other  layer,  and  continuous  with  the 
recurved  margin  of  the  superficial  perineal  fascia. 

The  superior  (deep)  layer  consists  of  right  and  left 
lateral  halves,  separated  in  the  middle  line  by  the 
urethra  close  to  the  prostate,  and  continuous  on  each 
side  with  the  fascia  covering  the  obturator  internus 
muscle.  The  levator  ani  muscle  is  between  this  layer 
and  the  rectovesical  fascia. 


MUSCLES    AND    FASCIiE    OF    THE   UPPER 
EXTREMITY 

Muscles  and  Fasciae  of  the  Shoulder 

The  Acromial  Region.— The  deep  fascia  is  strong  and 
tendinous  over  the  back  of  the  deltoid  and  infra- 
spinatus; the  infraspinatus  fascia  covers  the  teres 
minor  and  splits  at  the  posterior  border  of  the  deltoid, 
a  deep  layer  passing  to  the  shoulder-joint  under  that 
muscle,  a  superficial  layer  to  the  spine  of  the  scapula 
over  thf^  muscle. 

Deltoid. — Origin  in  three  portions :  an  anterior  from 
the  front  of  the  outer  third  of  the  clavicle,  a  middle 
from  the  point  and  outer  edge  of  the  acromion,  a  pos- 
terior from  the  lower  border  of  the  scapular  spine  and 
triangular  surface  at  its  inner  end,  and  from  the  infra- 


148  MUSCLE  TISSUE 

spinatus  fascia.     These  converge  into  the  tendon  of 
insertion  into  the  deltoid  tubercle  of  the  humerus. 

The  Posterior  Scapular  Region. — ^The  muscles  of  this 
region  are  as  follows : 

Supraspinatus.  Teres  major. 

Infraspinatus.  Teres  minor. 

Supraspinatus. — ^This  arises  from  inner  part  of  the 
supraspinous  fossa  to  region  of  the  notch,  from  supra- 
spinous fascia  and  transverse  ligament;  adherent  to 
capsule  and  infraspinatus  tendon;  inserted  into  the 
upper  of  the  three  facets  on  the  great  tuberosity  of 
the  humerus. 

Infraspinatus. — It  arises  from  the  inner  two-thirds 
of  the  infraspinous  fossa,  and  under  surface  of  the 
spine  of  the  scapula,  the  fibers  converge  to  a  tendon 
concealed  within  the  muscle  and  inserted  into  the 
middle  facet  of  the  great  tuberosity.  It  may  be 
inseparably  connected  with  the  teres  minor. 

Teres  Minor. — Origin,  from  narrow  grooved  surface 
on  the  back  of  the  scapula  close  to  the  axillary  border, 
from  septa  between  it,  the  teres  major,  and  infra- 
spinatus; inserted  into  the  lowest  facet  on  the  great 
tuberosity  and  into  the  shaft  for  a  short  distance 
below. 

Teres  Major. — Is  a  thick  somewhat  flattened  muscle. 
Origin,  from  the  oval  surface  on  the  back  part  of  the 
inferior  angle  of  the  scapula,  and  the  fibrous  septa 
common  to  it,  and  the  teres  minor  and  infraspinatus; 
inserted,  by  a  flat  tendon  into  the  inner  ridge  of  the 
bicipital  groove  of  the  humerus. 

The  Anterior  Scapular  Region. — Subscajmlaris. — 
Origin,  by  muscular  and  tendinous  fibers  from  the 
venter  of  the  scapula  and  groove  along  the  axillary 
border,  insertion,  small  tuberosity  of  the  humerus 
and  into  the  shaft  for  a  short  distance.  As  in  the 
deltoid,  this  muscle  contains  two  sets  of  septa — one 


MUSCLES  AND  FASCIA  OF  UPPER  EXTREMITY  149 

from  the' origin,  and  one  from  the  insertion  for  attach- 
ment of  the  obHque  muscular  fibers.  Some  fibers 
from  the  axillary  border  of  the  muscle  are  usually 
inserted  into  the  capsule,  known  as  the  subscapularis 
minor. 

The  Muscles  and  Fasciae  of  the  Arm 

The  aponeurosis  of  the  arm  (deep  fascia)  is  thin  over 
the  biceps,  strong  over  the  triceps,  and  is  attached  to 
the  humerus,  intermuscular  septa. 

The  Muscles  of  the  Anterior  Humeral  Region. — ^The 
muscles  of  this  region  are: 

Biceps.  Coracobrachialis. 

Brachialis  anticus. 

Biceps. — Its  short  or  inner  head  arises  with  the  cora- 
cobrachialis from  the  tip  of  the  coracoid  process;  the 
long  head,  from  the  upper  end  of  the  glenoid  cavity; 
within  the  capsule  by  a  tendon  continuous  on  each 
side  with  the  glenoid  ligament;  these  two  heads  form 
a  belly  in  the  middle  and  lower  part  of  the  arm.  The 
tendon  of  insertion  is  slightly  twisted  and  attached 
to  the  back  part  of  the  tuberosity  of  the  radius,  sep- 
arated from  the  forepart  by  a  bursa.  From  the  inner 
side  of  the  tendon  a  part  branches  off  as  an  aponeurotic 
band  or  semilunar  fascia,  and  blends  with  the  deep 
fascia  of  the  forearm  stretched  across  the  brachial 
vessels  and  median  nerve. 

Coracobrachialis. — Origin,  tip  of  the  coracoid  between 
the  pectoralis  minor  and  short  head  of  the  biceps; 
insertion,  inner  border  and  inner  surface  of  the  humerus 
near  its  middle,  between  the  triceps  and  the  brachialis 
anticus. 

Brachialis  anticus. — Arises  from  the  lower  half  of 
the  front  of  the  humerus,  nearly  the  whole  of  the 
internal  intermuscular  septum,  and  upper  part  of  the 
external.    It  is  adherent  to  the  capsule  of  the  elbow- 


150  ,      MUSCLE  TISSUE 

joint,  and  often  sends  a  slip  into  it,  and  is  inserted  into 
the  inner  part  of  the  rough  surface  at  the  junction 
of  the  coronoid  process  with  the  shaft  of  the  uhia  and 
to  a  part  of  the  tubercle  of  the  uhia. 

The  Muscles  of  the  Posterior  Humeral  Region. — The 
muscles  of  this  region  are: 

Triceps.  Subanconeus. 

Triceps  occupies  the  entire  posterior  aspect  of  the 
humerus.  Three  heads  are  inserted  into  a  common 
tendon  occupying  the  posterior  surface  of  the  muscle 
from  the  middle  of  the  arm  to  the  elbow.  The  middle 
or  long  head  arises  from  the  inferior  glenoid  tubercle 
of  the  scapula  and  adjacent  portion  of  the  axillary 
border;  this  forms  the  middle  and  superficial  part  of 
the  muscle  and  ends  on  the  inner  margin  of  the  tendon. 
The  external  head  arises  above  the  spiral  groove  and 
from  an  aponeurotic  arch  of  the  external  intermuscular 
septum  as  it  crosses  it,  extending  to  the  teres  minor 
insertion  above,  and  inserted  into  the  upper  end  and 
outer  border  of  the  tendon.  The  internal  or  deep 
head  arises  from  the  whole  posterior  surface  of  the 
humerus  below  the  spiral  groove,  from  the  lower  part 
of  the  external  intermuscular  septum,  from  the  whole 
of  the  internal,  as  high  as  the  teres  major;  some  of  its 
fibers  are  inserted  directly  into  the  olecranon  process  of 
the  ulna,  but  most  join  the  deep  surface  of  the  tendon. 
The  common  tendon  is  inserted  into  the  tuberosity  of  the 
olecranon  process  of  the  ulna,  and  externally  a  band 
is  prolonged  over  the  anconeus  to  the  fascia  of  the 
forearm  and  posterior  border  of  the  ulna;  it  may  send 
a  slip  to  the  capsule. 

Muscles  and  Fasciae  of  the  Forearm 

The  superficial  fascia  is  most  distinct  at  the  elbow, 
contains  the  superficial  veins,  and  below  connects  the 
skin  with  the  palmar  fascia. 


MUSCLES  AND  FASCIA  OF  UPPER  EXTREMITY   151 

The  aponeurosis  of  the  forearm  (deep  fascia)  is 
composed  largely  of  transverse  fibers,  strengthened 
by  expansions  from  the  condyles  of  the  humerus, 
olecranon,  and  fascia  over  the  biceps  and  triceps.  It 
sends  in  a  thin  layer  between  the  superficial  and  deep 
muscles;  this  anterior  portion  of  the  fascia  forms  at 
the  wrist  the  anterior  annular  ligament,  w^hich  binds 
down  the  tendons  of  the  flexor  muscles.  The  posterior 
portion  sends  off  septa  between  the  muscles  and  forms 
the  posterior  annular  ligament,  which  firmly  holds  in 
position  the  tendons  of  the  extensor  muscles.  The 
tendon  of  the  palmaris  longus  muscle  is  the  only  one 
passing  in  front  of  the  anterior  annular  ligament. 

The  Anterior  Radioulnar  Region. — ^These  muscles  are 
described  as  a  superficial  set,  consisting  of  five;  and  a 
deep  group,  of  three. 

Superficial  Layer. — ^All  from  a  common  tendon 
in  the  following  order  from  without  in: 

Pronator  teres  arises  by  two  heads,  the  larger  from 
the  upper  part  of  the  inner  condyle  above  the  common 
tendon  and  from  the  common  tendon,  fascia,  and  inter- 
muscular septum;  second  head,  thin  and  deep,  from 
the  inner  margin  of  the  coronoid  process;  insertion, 
by  a  flat  tendon  on  the  middle  of  the  outer  surface  of 
the  radius.  The  ulnar  artery  is  beneath  this  muscle, 
and  the  median  nerve  between  its  heads. 

Flexor  carpi  radialis  arises  from  the  common  tendon, 
fascia  of  the  forearm,  and  septa  between  it  and  the 
pronator  teres,  palmaris  longus,  and  flexor  sublimis; 
tendon  begins  below  the  middle  of  the  forearm,  passes 
through  a  special  compartment  of  the  anterior  annular 
ligament  through  a  groove  in  the  trapezium;  inserted 
into  the  base  of  the  second  metacarpal  bone,  anterior 
surface,  and  usually  by  a  small  slip  to  the  base  of 
the  third. 

Palmaris  longus  is  placed  between  the  ulnar  and  radial 
flexors  of  the  carpus,  resting  upon  the  flexor  sublimis; 
arises  from  the  common  tendon,   fascia,   and  septa. 


152 


MUSCLE  TISSUE 


Fia.  6S 


Superficial  muscles  of  front  of  right 
forearm.     (Testut.) 


forming  a  short  muscular 
belly  ending  in  a  slender 
tendon,  inserted  into  the 
palmar  fascia,  and  sends 
a  slip  to  the  abductor 
pollicis,  sometimes  one  to 
the  little  finger  muscle. 

Flexor  caryi  vlnaris  (M. 
ulnaris  internus)  is  the 
innermost  of  the  super- 
ficial group;  arises  by  two 
heads,  one  from  the  com- 
mon tendon,  and  one  from 
the  inner  side  of  the  olec- 
ranon and  upper  two- 
thirds  of  the  posterior 
border  of  the  ulna  by  an 
aponeurosis  common  to  it, 
the  flexor  profundus  digi- 
torum  and  the  extensor 
carpi  ulnaris;  muscular 
fibers  end  in  a  tendon 
which  occupies  the  ante- 
rior margin  of  the  lower 
half  of  the  muscle;  pos- 
teriorly the  muscular  fibers 
continue  down  to  within 
an  inch  of  its  insertion; 
inserted  into  the  pisiform 
by  a  small  band  to  the 
anterior  annular  ligament. 

Flexor  siiblimis  digi- 
toruvi,  placed  behind  the 
preceding,  arises  by  three 
heads:  (1)  Inner  condyle 
by  the  common  tendon, 
fibrous  septa,  and  internal 
lateral  ligament;  (2)  inter- 
nal margin  of  the  coronoid ; 


MUSCLES  AND  FASCIA  OF  UPPER  EXTREMITY  153 

(3)  anterior  oblique  line  of  the  radius;  divided  below 
into  four  parts,  ending  in  tendons  inserted  into  the 
second  phalanges  of  the  four  inner  digits. 

The  Deep  Muscles. — Flexor  profundus  digitorum. 
— Origin,  the  upper  three-fourths  of  the  inner  and 
anterior  surface  of  the  ulna,  from  not  quite  the  ulnar 
half  of  the  interosseous  membrane  for  the  same  dis- 
tance, and  from  an  aponeurosis  attached  to  the  pos- 
terior border  of  the  ulna,  common  to  it,  the  flexor  and 
extensor  carpi  ulnaris.  Only  one  tendon  (for  the  index 
finger)  separates  above  the  wrist;  in  the  palm,  as  the 
tendons  diverge,  they  give  origin  to  the  lumbricales; 
over  the  first  and  second  phalanges  the  tendon  is 
bound  down  by  an  osseo-aponeurotic  sheath,  and  oppo- 
site the  first  phalanx  it  passes  through  an  opening  in 
the  flexor  sublimis  tendon,  and  is  finally  inserted  by  an 
expanded  end  into  the  base  of  the  third  or  last  phalanx. 

The  sheaths  of  the  flexor  tendons  are  opposite  the 
first  and  middle  phalanges,  and  formed  of  strong 
transverse  bands,  ligamenta  vaginalia;  opposite  the 
joints  the  bands  change  into  a  thin  membrane,  strength- 
ened by  oblique  decussating  fibers,  so  that  there  are 
annular  or  transverse  fibers,  and  crucial  or  oblique. 
The  sheath  has  a  synovial  lining  containing  small 
folds,  vincula  tendinum  or  ligamenta  mucosa,  passing 
between  the  tendons  and  bones. 

Flexor  longus  pollicis  arises  from  the  anterior  surface 
of  the  radius,  below  its  oblique  line  to  the  edge  of  the 
pronator  quadratus,  and  from  the  adjacent  part 
of  the  interosseous  membrane.  The  tendon  passes 
between  the  sesamoid  bones  of  the  thumb  and  enters 
a  canal  similar  to  that  of  the  other  flexors,  to  be 
inserted  into  the  base  of  the  last  phalanx  of  the 
thumb.  Its  complete  separation  from  the  flexor  pro- 
fundus is  characteristic  of  man. 

Pronator  quadratus,  just  above  the  WTist,  close  to 
the  bones  behind  the  last  two  muscles,  quadrilateral 
and  flat,  arises  from  the  pronator  ridge  and  inner  part 


154  MUSCLE  TISSUE 

of  the  anterior  surface  of  the  ulna  for  the  lower  fourth, 
and  from  the  inferior  from  the  radiocarpal  joint; 
inserted  into  the  anterior  surface  and  anterior  margin 
of  the  shaft  of  the  radius  for  a  little  less  than  its  fourth. 

The  Radial  Region. — Three  in  number,  from  the  lower 
third  of  the  arm  and  upper  third  of  the  forearm  in  an 
almost  continuous  row. 

Supinator  longiis  rises  from  the  upper  two-thirds 
of  the  external  supracondylar  ridge  of  the  humerus 
and  external  intermuscular  septum,  limited  above  by 
the  spiral  groove;  thin  fleshy  belly  ends  at  the  middle 
of  the  forearm  in  a  flat  tendon  which  expands  at  its 
insertion  into  the  outer  side  of  the  radius  at  the  base 
of  the  styloid  process. 

Extensor  carpi  radialis  longior  arises  from  the  lower 
third  of  the  external  supracondylar  ridge  and  external 
intermuscular  septum  and  a  few  fibers  from  the  com- 
mon tendon ;  inserted  into  the  radial  half  of  the  posterior 
surface  of  the  base  of  the  second  metacarpal. 

Extensor  Carpi  Radialis  Brevior. — Origin,  by  the 
common  extensor  tendon  from  the  outer  condyle, 
septa,  external  lateral  ligament,  fascia,  and  a  fibrous 
arch  over  the  radial  nerve  and  radial  recurrent  vessels; 
insertion,  into  the  radial  half  of  the  posterior  surface  of 
the  base  of  the  metacarpal  bone  of  the  middle  finger. 

The  Posterior  Radioulnar  Region.  —  Superficial 
Layer. — Extensor  Communis  Digitorum. — Origin,  com- 
mon extensor  tendon  from  the  external  condyle  of  the 
humerus,  orbicular  ligament,  fascia,  and  septa;  there 
are  three  fleshy  bellies,  the  innermost  divided  into  two, 
four  passing  under  the  posterior  annular  ligament; 
the  first  and  second  pass  to  the  index  and  middle 
fingers  connected  by  a  weak  band,  always  transverse; 
the  first  is  joined  by  the  extensor  indicis  tendon  at 
the  metacarpophalangeal  joint;  the  third  runs  to  the 
ring  finger  and  sends  a  slip  to  the  middle  finger  tendon; 
the  fourth  divides,  the  outer  larger  part  going  to  the 
ring  finger,  the  inner  part  joining  the  outer  division 


MUSCLES  AND  FASCIA  OP  UPPER  EXTREMITY  155 

of  the  extensor  minimi  digiti  tendon;  this  fourth  is 
the  smallest  tendon,  and  receives  muscular  fibers  as 
far  as  the  wrist. 

Opposite  the  metacarpophalangeal  joints  the  tendons 
are  bound  down  by  transverse  fibers  from  the  front 
of  the  joint,  ligamenta  dorsalia;  inserted  into  the  base 
of  the  last  phalanx. 

Extensor  minimi  digiti  arises  from  the  superficial  and 
deep  fascia  of  the  forearm,  from  the  orbicular  ligament, 
from  the  septa  between  it  and  common  and  ulnar  exten- 
sors; its  tendon  is  in  a  groove  between  the  radius  and 
ulna,  and  splits  into  two  on  the  back  of  the  hand,  the 
outer  being  joined  by  a  slip  from  the  fourth  common 
extensor  tendon,  and  both  parts  end  on  the  little 
finger,  like  the  other  extensor  tendons. 

Extensor  Carpi  Ulnaris  {Ulnaris  Externus). — Origin, 
common  tendon,  orbicular  ligament,  septa,  fascia  of 
the  forearm,  which  is  connected  with  the  elbow- 
joint  capsule,  and  anconeus.  Insertion,  tuberosity  of 
the  base  of  the  fifth  metacarpal.  A  bursa  is  under 
its  tendon  of  origin  in  one-fourth  of  the  cases. 

Anconeus  fills  the  space  between  the  triceps  and 
extensor  carpi  ulnaris;  is  flat  and  triangular,  covered 
by  fascia  connected  with  the  triceps ;  arises  by  a  narrow 
tendon  from  a  fossa  on  the  inner  and  posterior  part 
of  the  external  condyle;  upper  fibers  are  transverse,  the 
rest  pass  obliquely  down  and  into  the  radial  aspect  of 
the  olecranon  and  adjacent  upper  third  of  the  ulna. 

Deep  Layer. — Supinator  Brevis. — Origin,  external 
lateral  ligament,  orbicular  ligament,  supinator  ridge, 
oblique  line  of  the  ulna,  and  for  a  short  distance  on 
the  outer  border  of  the  ulna  from  the  fascia  covering 
it,  which  is  connected  with  the  external  condyle;  it 
regularly  consists  of  two  layers  separated  by  the 
posterior  interosseous  nerve;  the  superficial  one  rises 
by  aponeurotic  fibers,  the  other  by  muscular.  The 
fibers  pass  sling-like  around  the  upper  part  of  the 
radius  to  be  inserted  into  a  third  of  its  length,  limited 


156  MUSCLE  TISSUE 

by  the  anterior  and  posterior  oblique  lines  to  its  neck 
and  elbow-joint  capsule. 

Extensor  Ossis  Metacarpi  Pollicis. — Origin,  upper 
part  of  the  outer  division  of  the  posterior  surface  of 
the  ulna  below  the  supinator  brevis,  from  the  middle 
third  of  the  posterior  surface  of  the  radius  and  inter- 
osseous membrane  between.  Its  tendon  passes  over 
those  of  the  radial  extensors,  and  is  inserted  into  the 
radial  side  of  the  base  of  the  metacarpal  bone  of  the 
thumb,  and  commonly  by  a  slip  into  the  trapezium, 
its  tendon  usually  splitting. 

Extensor  longus  pollicis  arises  below  the  extensor 
ossis  on  the  middle  third  of  the  ulna  and  from  the 
interosseous  membrane  for  about  one  inch;  its  tendon 
passes  over  the  radial  extensors,  and  is  inserted  into 
the  posterior  aspect  of  the  base  of  the  last  phalanx  of 
the  thumb. 

Extensor  Indicis  Proprius. — Origin,  from  the  ulna 
below  the  extensor  longus  pollicis,  and  slightly  from 
the  interosseous  membrane  and  fascia  over  the  exten- 
sor carpi  ulnaris;  unites  with  the  common  extensor 
tendon  for  the  index,  and  forms  the  usual  insertion. 
This  and  the  extensor  minimi  digiti  tendon  are  always 
on  the  ulnar  side  of  the  respective  common  extensor 
tendons. 

Extensor  Brevis  Pollicis. — Origin,  small  part  of  the 
interosseous  membrane  and  radius  below  the  middle, 
next  below  the  extensor  ossis;  insertion,  upper  end  of 
the  first  phalanx  of  the  thumb  on  its  posterior  aspect. 

The  Muscles  and  Fascise  of  the  Hands 

Fascia  of  the  posterior  aspect  is  a  thin  layer  prolonged 
from  the  posterior  annular  ligament  and  blending  with 
the  extensor  expansions  over  the  fingers;  deeper  than 
this  the  interossei  are  covered  by  thin  aponeuroses. 

Fascia  of  the  palm  consists  of  a  strong  central 
part  and  two  lateral  portions  which  cover  the  short 


MUSCLES  AND  FASCIA  OF  UPPER  EXTREMITY  157 

muscles  of  the  thumb  and  little  finger.  The  central 
portion  is  the  part  commonly  called  the  palmar  fascia; 
it  consists  of  fibers  mostly  prolonged  from  the  palmaris 
longus,  some  from  the  annular  ligament,  thus  form- 
ing two  superficial  layers  with  vertical  fibers,  between 
which  is  the  palmaris  brevis  muscle;  there  is  a  deep 
layer  of  transverse  fibers.  Below,  the  fascia  divides 
into  four  processes  to  join  the  digital  sheaths;  offsets 
are  sent  back  to  the  deep  transverse  ligament  at  the 
heads  of  the  metacarpals,  forming  a  short  canal  above 
each  finger  for  the  flexors.  Between  the  processes 
the  transverse  layer  of  fascia  covers  the  lumbrical 
muscles,  digital  vessels,  and  nerves,  passing  over 
to  the  thumb  and  forefinger.  At  the  clefts  of  the 
fingers  a  transverse  band  is  called  the  superficial 
transverse  ligament,  or  Gerdy's  fibers.  The  interossei 
muscles  also  have  a  separate  fascia  continued  below 
into  the  deep  transverse  ligament. 

The  Radial  Region. — The  following  muscles  consti- 
tute the  thenar  eminence  (the  fleshy  prominence  of  the 
palm  corresponding  to  the  base  of  the  thumb)  and 
have  a  great  variety  of  description. 

Abductor  pollicis.  Adductor  pollici^  obHquus. 

Flexor  brevis  pollicis.     Adductor  trans  versus 
Opponens  pollicis.  pollicis. 

The  Ulnar  Region. — ^The  following  muscles  constitute 
the  hypothenar  eminence.  (The  fleshy  prominence  of 
the  palm  corresponding  to  the  fleshy  part  over  the 
metacarpal  bone  of  the  little  finger.) 

Abductor  minimi  digiti.  Opponens  minimi  digiti. 

Flexor  brevis  minimi  digiti.       Palmaris  brevis. 

The  Middle  Palmar  Region. — The  dorsal  interossei 
are  four  in  number,  one  for  each  space,  not  rising 
above  the  level  of  the  bones,  and  numbered  from 
without    inward.      Each    rises    from    the   two   bones 


158  MUSCLE  TISSUE 

between  which  it  is  placed,  most  extensively  from 
that  supporting  the  finger  upon  which  it  acts.  The 
tendon  is  inserted  partly  into  the  base  of  the  first 
phalanx  and  partly  into  the  extensor  tendon. 

The  palmar  interossei  are  three  in  number,  are  adduc- 
tors, and  each  rises' from  the  lateral  surface  of  the  meta- 
carpal of  the  finger  on  which  it  acts.  They  terminate 
like  the  posterior  tendons.  The  first  belongs  to  the 
ulnar  side  of  the  index,  the  second  and  third  to  the 
radial  sides  of  the  ring  and  little  fingers. 

The  lumbricales  are  four  small  muscles,  not  always 
well-defined.  They  arise  from  the  tendons  of  the  flexor 
profundus  digitorum. 

Actions  of  Muscles  of  the  Forearm  and  Hand. 
— Pronation  by  the  pronator  teres  and  quadratus 
and  flexor  carpi  radialis  slightly;  pronator  teres 
flexes  the  forearm;  can  only  pronate  when  the  radius 
is  intact. 

Supination  by  the  supinator  brevis,  biceps,  and 
supinator  longus;  the  latter  is  a  flexor  of  the  elbow 
and  brings  the  forearm  into  midsupination.  Radial 
extensors  of  the  wrist  flex  the  elbow;  others  from  the 
external  condyle  extend. 

Flexion  #/  the  tvrist  by  the  flexor  carpi  ulnaris  and 
radialis,  by  the  flexors  of  the  fingers  and  palmaris 
longus. 

Extension  of  the  wrist  by  the  extensor  carpi  ulnaris, 
the  two  radial  extensors,  and  extensors  of  the  fingers. 

Abduction  of  the  wrist  by  the  radial  flexor  and  radial 
extensors  and  extensors  of  the  thumb. 

Adduction  of  the  wrist  by  the  flexor  and  extensor 
carpi  ulnares.  The  flexor  carpi  radialis  and  extensor 
carpi  ulnaris  act  on  the  radiocarpal  joint;  the  flexor 
carpi  ulnaris  and  radial  extensors  on  the  midcarpal 
joint. 

The  extensors  of  the  wrist  are  moderators  of  the 
long  flexors  of  the  fingers;  the  flexors  of  the  wrist 
are  moderators  of  the  extensors  of  the  fingers. 


MUSCLES  AND  FASCIJE  OF  LOWER  EXTREMITY  159 

The  posterior  interossei  abduct  the  fingers  from  the 
middle  one;  the  palmar  adduct;  the  interossei  and 
lumbricales  flex  the  first  phalanx  and  extend  the  last 
two. 

Flexion  in  the  fingers.  Extension  in  the  fingers. 

First  phalanx,  by  the  interossei  By  the  extensor  communis, 

and  lumbricales. 

Second  phalanx,   by  the  flexor  By  the  interossei   and  lumbri- 

sublimis.  cales. 

Third    phalanx,    by    the    flexor  By  the   interossei   and  lumbri- 

profundus.  cales. 

When  we  flex  the  fingers  they  tend  to  approach,  due 
to  the  lateral  ligaments  and  obliquity  of  the  tendons. 

The  palmaris  longus  makes  tense  the  palmar  fascia, 
feebly  flexes  the  forearm  and  wrist;  all  the  muscles 
from  the  condyle  feebly  flex  the  forearm. 

Palmaris  brevis  wrinkles  the  skin  over  the  hypothe- 
nar  eminence  and  protects  the  ulnar  vessels  and  nerve 
from  pressure  when  a  foreign  body  is  grasped. 

Extension  in  the  thumb  is  in  the  plane  of  abduction 
of  the  fingers,  and  its  abduction  is  a  movement  forward. 
The  action  of  its  muscles  and  those  of  the  little  finger 
are  indicated  by  their  names;  the  flexors  of  the  first 
phalanx  in  either  case  also  extend  the  last,  as  the  inter- 
ossei would.  The  ulnar  extensor  and  flexor  of  the 
carpus  are  moderators  of  the  thumb  extensors.  There 
are  three  flexors  of  the  wrist  (including  the  palmaris 
longus)  and  three  extensors,  three  flexors  of  the  fingers 
and  three  extensors,  three  flexors  of  the  thumb  and 
three  extensors. 


THE   MUSCLES    AND    FASCIiE   OF   THE   LOWER 
EXTREMITY 

Fasciae  of  the  Thigh 

The  superficial  fascia   is  continuous  with   that  of 
other  parts  of  the  body. 


160  MUSCLE  TISSUE 

The  deep  fascia  or  fascia  lata  is  a  strong  membrane 
forming  a  continuous  sheath  around  the  limb.  It 
descends  on  the  gluteus  medius  as  far  as  the  upper 
border  of  the  gluteus  maximus,  which  muscle  it  encases, 
and  over  the  great  trochanter  a  great  part  of  the  muscle 
is  inserted  between  its  layers.  From  the  forepart 
of  the  iliac  crest  to  the  outer  tuberosity  of  the  tibia 
is  the  iliotibial  band,  w^hich  receives  the  insertions 
of  the  tensor  vaginae  femoris  and  gluteus  maximus 
muscles. 

The  fascia  lata  has  various  deep  processes;  one  is 
internal  to  the  tensor  vaginae  femoris  on  the  surface 
of  the  vastus  externus. 

There  are  external  and  internal  intermuscular  septa 
inserted  into  the  linea  aspera. 

The  Gluteal  Region  (Buttocks) 

Gluteus  Maximus. — A  quadrilateral,  very  coarse 
muscle.  Origin,  posterior  fourth  of  the  external  lip 
of  the  iliac  crest  and  rough  surface  between  it  and  the 
posterior  gluteal  line,  the  last  two  pieces  of  the  sacrum 
and  first  three  of  the  coccyx,  great  sacrosciatic  liga- 
ment, and  aponeurosis  of  the  erector  spinae. 

The  upper  half  and  superficial  fibers  of  the  lower  half 
are  inserted  into  the  fascia  lata  and  continued  into  the 
iliotibial  band;  the  deeper  portion  of  the  low^er  half 
into  the  gluteal  ridge  on  the  upper  third  of  the  shaft 
of  the  femur. 

Gluteus  Medius. — Origin,  ilium  between  the  crest, 
the  posterior  and  middle  curved  lines,  and  from  the 
fascia  covering  it;  to  insert  on  the  outer  surface  of  the 
great  trochanter;  a  small  bursa  between  the  bone  and 
tendon. 

Gluteus  minimus  is  covered  by  the  preceding,  and 
arises  from  the  whole  surface  on  the  ilium  between  the 
middle  and  inferior  curved  lines,  fibers  converge  into 
an  aponeurotic  tendon  on  the  outside  of  the  muscle, 


MUSCLES  AND  FASCIA  OF  LOWER  EXTREMITY   IGl 

inserted  into  an  impression  on  the  front  of  the  great 
trochanter. 

Actions  of  the  glutei  on  the  lower  limb: 

Flexion.  Extension. 

Glut,  med.,  anterior  fibers.  Glut,  maximus. 

Glut,  min.,  anterior  fibers.  Glut,  med.,  posterior  fibers. 

Glut,  min.,  posterior  fibers. 

Adduction.  Abduction. 

Glut,   med.,   anterior  fibers   (in         Glut.,  max.,  slight. 

sitting  posture.  fstrong,  whole 

Glut,   min.,   anterior  fibers    (in         Glut.  med.  I      muscle,  espe- 
sitting  posture).  Glut.  min.  jcially  mid- 

(     portion. 

Rotate  in.  Rotate  out. 

Glut,  med.,  anterior  fibers.  Glut.  max. 

Glut,  min.,  anterior  fibers.  Glut,  med.,  posterior  fibers. 

Glut,  min.,  posterior  fibers. 

The  gluteus  maximus  extends  the  trunk  on  the  thigh 
as  in  ascending  stairs;  in  walking  it  is  not  used,  as  the 
erect  position  is  maintained  by  ligaments;  steadies 
and  supports  the  knee  by  the  iliotibial  band. 

The  iliopsoas  flexes  the  thigh  and  rotates  out;  flexes 
the  body  on  the  thigh;  the  psoas  bends  the  lumbar 
spine  forward  and  laterally. 

Psoas  parvus  makes  tense  the  iliac  fascia. 


The  Thigh  Muscles 

These  are  arranged  in  three  sets — anterior,  poste- 
rior, and  internal,  with  superficial  and  deep  layers,  the 
former  passing  over  two  joints,  the  latter  over  one. 

The  Anterior  Femoral  Region. —  Tensor  vaginoe  femoris 
(tensor  fasciae)  lies  in  a  groove  between  the  gluteus 
medius,  rectus,  and  sartorius.  Origin,  anterior  part 
of  the  external  lip  of  the  iliac  crest,  notch  between 
the  two  spines;  insertion,  between  the  two  layers  of 
the  fascia  lata  three  or  four  inches  below  the  great 
trochanter,  and  from  the  insertion  fibers  are  prolonged 
into  the  iliotibial  band. 


162  MUSCLE  TISSUE 

Sartorius  (Tailor  Muscle). — Origin,  anterior  superior 
spine  of  the  ilium  and  small  part  of  the  notch  imme- 
diately below;  insertion,  inner  surface  of  the  tibia  near 
the  tubercle,  sending  an  expansion  from  the  upper 
border  to  the  capsule,  one  from  the  lower  border  to 
the  fascia  of  the  leg,  and  one  to  the  tibia  behind  the 
tendons  of  the  gracilis  and  semitendinosus. 

Quadriceps  Femoris. — Largest  muscle  of  the  body, 
four  parts  closely  united,  (a)  Rectus  femoris,  in  a 
straight  line  from  the  pelvis  to  the  patella.  Origin, 
by  two  heads,  anterior  one  from  the  anterior  inferior 
spine,  and  posterior  from  the  impression  just  above 
the  acetabulum;  they  join  at  an  angle  of  60  degrees 
close  below  the  acetabulum;  the  tendon  is  anterior 
above,  then  in  centre  of  the  muscle.  The  lower  tendon 
becomes  free  three  inches  above  the  patella;  is  attached 
to  the  upper  margin  of  that  bone,  and  helps  form  the 
common  tendons. 

(b)  The  vastus  externus  is  the  outer  part  of  the  quad- 
riceps. Origin,  narrow  and  aponeurotic  from  the  upper 
half  of  the  anterior  intertrochanteric  line,  outer  part 
of  the  root  of  the  great  trochanter,  outer  side  of  the 
gluteal  ridge,  upper  half  of  the  outer  lip  of  the  linea 
aspera,  from  external  intermuscular  septum,  and  a 
strong  aponeurosis  extending  over  the  upper  two- 
thirds  of  the  muscle.  Aponeurosis  of  insertion  occupies 
the  deep  surface  of  the  muscle,  joins  the  common 
tendon,  and  sends  expansion  to  the  lateral  patellar 
ligaments  and  rectus  tendon. 

(c)  The  vastus  internus  arises  from  a  superficial 
aponeurosis  and  deeper  fibers  from  the  spiral  line, 
inner  lip  of  the  linea  aspera,  and  from  tendons  of  the 
adductor  longus  and  magnus;  they  end  in  a  deep 
aponeurosis  which  enters  the  common  tendon.  Its 
muscular  fibers  pass  lower  than  those  of  the  externus, 
and  are  inserted  into  the  inner  margin  of  the  patella, 
some  into  the  rectus  tendon. 

Crureus  arises  from  upper  two-thirds  of  the  anterior 


MUSCLES  AND  FASCIA  OF  LOWER  EXTREMITY  163 

surface  of  the  femur,  outer  surface  of  the  femur  in 
front  of  and  below  the  vastus  externus,  lower  half 
of  the  external  intermuscular  septum;  fibers  end  in  a 
superficial  aponeurosis  which  forms  the  deepest  portion 
of  the  common  terdon.  They  arise  from  a  series  of 
transverse  arches  with  intervening  bare  spaces  on 
the  front  of  the  femur.  Between  the  crureus  and  the 
vastus  internus  most  of  the  internal  surface  of  the  bone 
is  free. 

The  common  or  siiprapatellar  tendon  is  inserted  into 
the  forepart  of  the  upper  border  of  the  patella,  and  a 
few  fibers  are  prolonged  over  its  anterior  surface  into 
the  ligamentum  patellse.  A  large,  thick  ligament  sur- 
rounding the  patella  and  inserted  into  the  tubercle  of 
the  tibia. 

Subcrureus  is  the  name  of  a  few  fibers  which  may  be 
regarded  as  the  deepest  layer  of  the  crureus.  Origin, 
anterior  surface  of  the  femur  in  the  lower  fourth; 
insertion,  separated  by  a  fat  layer  from  the  vasti  into 
the  synovial  membrane  of  the  knee-joint. 

Hunter's  canal  is  a  three-cornered  passage  in  the 
middle  two-fourths  of  the  thigh,  in  the  angle  between 
the  adductors  magnus  and  longus  and  vastus  internus. 
It  is  made  a  canal  by  a  bridge  of  fascia,  and  contains 
the  femoral  artery,  vein,  and  long  saphenous  nerve. 

Nerves. — ^Anterior  crural  for  the  quadriceps  and 
sartorius;  superior  gluteal  for  the  tensor  vaginae  femoris. 

Actions. — Satorius  flexes  the  hip  and  knee  with 
e version  of  the  thigh;  rotates  the  leg  inward. 

Quadriceps  femoris  extends  the  leg;  not  necessary 
for  the  maintenance  of  the  erect  attitude. 

Rectus  femoris  also  flexes  the  hip;  its  posterior  head 
is  tense  when  the  thigh  is  bent.  Lower  fibers  of  the 
vastus  internus  draw  the  patella  in. 

Tensor  vaginoB  femoris  rotates  the  thigh  in  and 
abducts,  assisted  by  the  gluteus  maximus;  counter- 
acts the  gluteus  maximus,  which  tends  to  draw  the 
iliotibial  band  backward. 


164  MUSCLE  TISSUE 

The  Posterior  Femoral  Region  (Hamstrings). — Biceps 
Femoris. — Origin,  long  head  by  a  tendon  common  to 
it  and  semitendinosus  from  inner  impression  on  the 
lower  part  of  the  ischial  tuberosity,  and  from  the 
sacrosciatic  ligament;  short  head  from  the  lower  two- 
thirds  of  the  outer  lip  of  :the  linea  aspera  and  external 
intermuscular  septum;  fibers  from  both  heads  end 
in  a  tendon  inserted  into  the  upper  and  outer  part  of 
the  head  of  the  fibula  by  two  portions  embracing  the 
external  lateral  ligaments. 

Semitendinosus. — Arises  from  the  tuberosity  of  the 
ischium  and  tendon  common  to  it  and  biceps  for  3 
inches.  Terminates  in  the  lower  third  of  the  thigh  in 
a  long,  slender  tendon,  and  curves  forward  in  an  ex- 
panded form  to  insert  on  the  upper  part  of  the  inner 
surface  of  the  tibia  or  anterior  crest  of  the  tibia,  and 
sends  a  process  to  the  fascia  of  the  leg. 

Semimembranosus. — Origin,  tuberosities  of  the  ischium 
above  and  outside  the  tendon  of  the  biceps  and  semiten- 
dinosus, and  its  tendon  is  grooved  posteriorly  for  the 
common  tendon  of  those  two  muscles.  Tendon  of  origin 
is  on  the  outer  side  of  the  muscle  for  three-fourths  the 
length  of  the  thigh ;  tendon  of  insertion,  on  the  opposite 
side  of  the  muscle,  and  turns  forward  and  is  inserted  by 
four  parts:  (1)  into  a  horizontal  groove  on  the  back  of 
the  inner  tuberosity  of  the  tibia;  (2)  expansion  is  sent 
up  and  in  as  the  posterior  oblique  ligament  of  the  knee- 
joint;  (3)  down  to  the  fascia  over  the  popliteus  muscle; 
(4)  to  form  the  short  internal  lateral  ligament  of  the 
knee-joint. 

-The  Internal  Femoral  Region. — Pectineus. — Origin, 
iliopectineal  line,  and  slightly  from  bone  in  front  of 
this,  and  from  the  fascia  over  the  muscle;  insertion, 
femur  behind  the  small  trochanter  and  upper  part 
of  the  line  passing  from  this  trochanter  to  the  linea 
aspera. 

Adductor  Longus. — Flat  and  triangular,  internal  to 
the  pectineus,  on  same  plane.    Origin,  short  tendon 


Fia.  70 


Muscles  in  the  dorsum  of  the  right 
thigh.     (Testut.) 


Adductores  magnus  and  brevis  of 
the  right  side.     (Testut.) 


166  MUSCLE  TISSUE 

from  the  body  of  the  pubis  below  the  crest  and  near 
the  angle;  insertion,  inner  lip  of  the  linea  aspera,  united 
to  the  vastus  internus  in  front  and  adductor  magnus 
behind. 

Gracilis. — Origin,  inner  margin  of  pubic  bone  and  a 
portion  of  its  inferior  ramus ;  thin  and  flat,  then  narrow 
and  thicker.  A  round  tendon  in  the  lower  third  of  the 
thigh,  curving  forward  below,  inserted  into  the  inner 
side  of  the  tibia  just  above  the  semitendinosus,  and 
covered  by  the  sartorius. 

Adductor  Brevis. — Origin,  body  and  inferior  ramus  of 
the  pubis  below  the  adductor  longus,  between  the  gra- 
cilis and  obturator  externus;  insertion,  into  the  whole 
line  from  the  small  trochanter  to  the  linea  aspera 
behind  the  pectineus.  It  lies  between  the  adductor 
magnus  and  longus. 

Adductor  Femoris  Minirnus. — This  is  what  is  de- 
scribed with  the  adductor  magnus,  usually  as  its 
anterior  and  superior  portion.  Origin,  body  of  the 
pubis  and  ischiopubic  rami;  insertion,  femur,  in  a  line 
from  the  quadratus  femoris  to  the  upper  end  of  the 
linea  aspera,  and  a  short  distance  along  it. 

Adductor  Magnus. — Origin,  ischial  ramus  internal 
to  the  above  muscle  and  outer  half  of  the  triangular 
space  on  the  posterior  inferior  surface  of  the  tuberosities 
of  the  ischii;  fibers  pass  in  two  layers,  one  to  the  inner 
lip  of  the  linea  aspera,  and  the  other  on  the  inner  side 
of  the  opening  for  the  femoral  vessels  by  a  distinct 
rounded  tendon  to  insert  on  the  adductor  tubercle  on 
the  inner  condyle  of  the  femur.  The  femoral  attach- 
ment is  interrupted  by  three  or  four  tendinous  arches 
for  the  perforating  arteries. 

Actions. — All  adduct  the  thigh.  Pectineus,  adductor 
longus  and  brevis  flex  the  hip,  while  part  of  adductor 
magnus  from  the  ischial  tuberosity  to  the  condyle 
may  extend  the  thigh  and  rotate  in.  Gracilis  flexes 
the  knee  and  rotates  the  leg  inward.  Adductors  and 
opponens,  the  gluteals,  balance  the  body  in  walking. 


MUSCLES  AND  FASCIA  OF  LOWER  EXTREMITY  167 

(1)  Anterior  fibers  of  the  gluteus  medius  (2)  and 
minimus;  (3)  tensor  vaginae  femoris;  and  some  say  (4) 
the  condylar  part  of  the  adductor  magnus,  rotate  the 
thigh  inward. 

Muscles  of  the  Leg 

The  Anterior  Tibiofibular  Region  (Extensors). —  Tibi- 
alis Anticus. — Origin,  outer  tuberosity  of  the  tibia, 
upper  half  of  the  outer  surface  of  that  bone,  and 
adjacent  interosseous  membrane,  fascia  of  the  leg, 
and  intermuscular  septum;  insertion,  oval  mark  on  the 
inner  and  lower  part  of  the  internal  cuneiform  and  first 
metatarsal  dividing  into  two  slips. 

Extensor  Longus  or  Proprius  Hallucis.  —  Origin, 
middle  two-fourths  of  the  narrow  anterior  surface  of 
the  fibula  and  contiguous  portion  of  the  interosseous 
membrane;  insertion,  base  of  the  terminal  phalanx  of 
the  great  toe  on  the  dorsal  aspect.  It  spreads  in  an 
expansion  on  each  side  over  the  metatarsophalangeal 
articulation,  and  almost  always  sends  a  slip  to  the 
base  of  the  first  phalanx. 

Extensor  Longus  Digitorum  Pedis. — Origin,  external 
tuberosity  of  the  tibia,  head,  and  upper  two-thirds  of 
the  anterior  surface  of  the  fibula,  very  largely  from 
the  septa  and  fascia  and  interosseous  membrane  above 
the  origin  of  the  extensor  proprius  hallucis.  Tendon 
divides  into  four  slips  for  the  outer  four  toes.  They 
are  continued  into  expansions  which  are  joined  on 
the  first  phalanx  by  processes  from  the  interossei 
and  lumbricales.  They  divide  into  three  parts — the 
middle  inserted  into  the  middle  phalanx;  the  lateral 
parts  unite,  and  are  inserted  into  the  base  of  the 
terminal  phalanx  as  in  case  of  the  extensors  of  the 
fingers. 

Peroneus  Tertius. — Origin,  lower  third  or  more  of 
the  anterior  surface  of  the  fibula,  from  the  interosseous 
membrane,   from    the   septum   between    it    and    the 


168  MUSCLE  TISSUE 

peroneiis  brevis;  insertion,  upper  surface  of  the  base 
of  the  fifth  metatarsal,  sometimes  the  fourth.  This 
muscle  is  peculiar  to  man. 

The  Fibular  or  Peroneal  Region. — Peroneus  Longus. — 
Origin,  head  and  upper  two-thirds  of  the  external 
surface  of  the  fibula,  fascia  of  the  leg,  and  septa  on 
each  side.  Tendon  begins  in  the  lower  half  of  the  leg, 
passes  behind  the  external  malleolus;  then  forward  on 
the  outer  side  of  the  os  calcis,  winds  around  the  tuber- 
osity of  the  cuboid,  and  enters  its  groove,  crosses  the 
sole  obliquely,  and  is  inserted  into  the  outer  side  of 
the  tuberosity  of  the  first  metatarsal,  and  slightly 
into  the  internal  cuneiform;  a  frequent  offset  to  the 
base  of  the  second  metatarsal  and  first  dorsal  inter- 
osseous. 

Peroneus  Brevis. — It  lies  deeper  than  the  peroneus 
longus.  Origin,  lower  two-thirds  of  the  external  surface 
of  the  fibula  from  the  septa  and  a  flat  tendon  on  the 
surface  turned  toward  the  bone;  insertion,  tuberosity 
at  the  base  of  the  fifth  metatarsal,  sending  a  small  slip 
to  the  outer  edge  of  the  extensor  of  the  little  toe  or 
forepart  of  the  metatarsal  bone. 

The  Posterior  Tibiofibular  Region  (Flexors). — Super- 
ficial Muscles. — Gastrocnemius, — Gastrocnemius  has 
two  large  heads  from  the  femur,  terminating  at  the 
middle  of  the  leg  in  a  common  tendon.  Outer  head 
from  the  depression  on  the  outer  side  of  the  external 
condyle  above  the  tuberosity,  and  from  the  posterior 
surface  of  the  femur  just  above  that  condyle.  Inner 
head  from  the  upper  part  of  the  internal  condyle. 
The  two  heads  join  with  the  soleus  and  are  inserted 
into  the  tendo  Achillis. 

Soleus.  —  Origin,  externally  from  the  posterior  sur- 
face of  the  head  and  upper  third  of  the  shaft  of  the 
fibula;  internally,  oblique  line  and  inner  border  of  the 
tibia  to  its  middle,  and  from  a  tendinous  arch  over 
the  popliteal  vessels  and  nerve;  fibers  rise  to  a  large 
extent   from   two   tendinous   laminae   which   descend 


MUSCLES  AND  FASCIA  OF  LOWER  EXTREMITY   169 

in  the  muscle,  one  from  the  fibula  and  one  from  the 
tibia.  Fibers  from  the  anterior  surfaces  of  these  laminae 
converge  to  a  median  septum;  fibers  from  their  pos- 
terior surfaces  pass  down  and  back  to  an  aponeurosis 
covering  the  back  surface  of  the  muscle.  The  tendon 
of  insertion  is  prolonged  from  this  aponeurosis,  joined 
by  the  median  septum.  Muscular  fibers  are  continued 
down  on  the  deep  surface  of  the  tendo  Achillis  near 
to  the  heel. 

The  gastrocnemius  and  soleus  form  the  calf  of  the  leg. 

Tendo  Achillis,  broad  at  fir«!t,  contracts  to  within 
IJ  inches  of  the  heel,  then  expands,  and  is  inserted 
into  the  middle  and  lower  parts  of  the  posterior  surface 
of  the  tuberosity  of  the  os  calcis,  a  bursa  having  all 
the  characters  of  a  synovial  membrane,  with  vascular 
and  fatty  synovial  tufts,  separating  it  from  the  upper 
part  of  this  surface. 

Plantaris. — Origin,  femur  above  the  external  condyle 
and  from  the  posterior  ligament  of  the  knee-joint. 
Muscular  belly  3  to  4  inches  long,  and  the  long,  slender 
tendon  turns  in  between  the  gastrocnemius  and  soleus 
to  the  inner  border  of  the  tendo  Achillis,  and  inserted 
by  its  side  into  the  os  calcis. 

Popliten^. — Origin,  round  tendon,  one  inch  long,  from 
the  groove  on  the  outer  surface  of  the  external  condyle 
of  the  femur,  within  the  capsule  of  the  joint,  in  contact 
with  the  semilunar  cartilage,  and  by  muscular  fibers 
from  the  ligamentum  popliteus  arcuatum.  Fibers 
pass  down  and  are  inserted  into  the  triangular  surface 
of  the  tibia  above  the  oblique  line,  and  into  the 
aponeurosis  over  the  muscle. 

The  Deep  Muscles  {Flexors)  .—Flexor  Longus  Bigi- 
torum  Pedis. — Origin,  inner  portion  of  the  posterior 
surface  of  the  tibia  for  the  middle  two-fourths  of  its 
length,  from  the  aponeurosis  over  the  tibialis  posticus. 
Descends  behind  the  internal  malleolus  of  the  tibia, 
passes  forward  and  obliquely  outward,  having  crossed 
the  tibialis  posticus  tendon  in  the  leg,  and  now  crossing 


170  MUSCLE  TISSUE 

that  of  the  flexor  longus  hallucis,  in  each  case  super- 
ficially. It  divides  into  four  parts  for  terminal  phalanges 
of  the  four  lesser  toes. 

Tibialis  Posticus,  beneath  the  two  long  flexors. 
Origin,  posterior  surface  of  the  interosseous  membrane, 
outer  part  of  the  posterior  surface  of  the  tibia  below 
the  oblique  line  of  the  middle  of  the  bone,  whole  inner 
surface  of  the  fibula,  and  from  the  aponeurosis  over  it. 
Tendon  along  the  inner  border  of  the  muscle,  free  at 
the  level  of  the  lower  tibiofibular  articulation,  passes 
behind  the  inner  malleolus,  inserted  into  the  tuberosity 
of  the  scaphoid,  with  offsets  to  the  three  cuneiform, 
to  cuboid,  to  bases  of  the  second,  third,  and  fourth 
metatarsals,  and  to  the  transverse  tarsal  ligament  and 
flexor  longus  hallucis  tendon,  and  sends  a  thin  process 
back  to  the  sustentaculum  tali  of  the  os  calcis. 

Flexor  Longus  Hallucis. — Origin,  lower  two-thirds  of 
the  posterior  surface  of  the  fibula,  septum  between  it 
and  the  peronei ;  aponeurosis  common  to  it  and  flexor 
longus  digitorum.  Tendon  at  the  posterior  surface 
of  the  muscle  traverses  groove  on  the  back  of  the 
astragalus  and  under  surface  of  the  sustentaculum, 
gives  slip  to  the  flexor  longus  digitorum  in  the  sole 
of  the  foot,  and  proceeds  to  the  base  of  the  terminal 
phalanx  of  the  great  toe. 

Muscles  of  the  Foot 

The  Dorsal  Region  (Instep). — Extensor  Brevis  Digi- 
torum Pedis. — Arises  from  forepart  and  upper  and  outer 
surface  of  the  os  calcis,  in  front  of  the  groove  for  the 
peroneus  brevis  tendon,  and  from  the  anterior  ligament 
of  the  ankle.  The  tendon  has  several  vertical  leaflets 
from  which  muscular  fibers  arise,  dividing  into  three 
bellies  w^hich  unite  with  the  outer  border  of  the  long 
extensors  for  the  second,  third,  and  fourth  toes. 

The  Plantar  Region  (Sole). — The  Central  Group. — 
Flexor  Brevis  Digitorum  and  Flexor  Accessorius  Lum- 
bricales. — Four  in  number.    Origin,  at  points  of  division 


MUSCLES  AND  FASCIA  OF  LOWER  EXTREMITY   171 

of  the  flexor  longus  digitorum  tendon,  each  attached 
to  two  tendons,  except  the  most  internal  one;  they  pass 
to  the  inner  side  of  the  four  outer  toes;  inserted  into 
the  bases  of  the  first  phalanges. 

The  Internal  Group. — Abductor  Hallucis,  flexor 
brevis  hallucis,  and  adductor  hallucis  (oblique  trans- 
verse portions). 

The  External  Group. — Abductor  Minimi  Digiti, 
and  flexor  brevis  minimi  digiti. 

Actions.^ Popliteus  flexes  the  knee  and  rotates  the 
leg  inward,  pulls  on  the  capsule  of  the  joint,  and  keeps 
the  popliteal  bursa  open.  The  dorsum  of  the  foot 
and  anterior  surface  of  the  leg  is  the  extensor  surface; 
the  opposite  side  is  the  flexor  surface,  so  that  raising 
the  foot  toward  the  front  of  the  leg  is  really  extension, 
and  depressing  it  is  flexion;  it  is  customary  to  apply 
reverse  terms  to  these  acts. 

Gastrocnemius  flexes  the  knee,  extends  the  ankle, 
combines  with  the  soleus,  and  lifts  the  heel  or  raises 
the  body  on  toes. 

Tibialis  anticus  and  peroneus  tertius  flex  the  ankle; 
the  former  rotates  inward,  adducts,  raises  the  first 
metatarsal  bone. 

Tibialis  posticus,  peroneus  longus  and  brevis  are 
extensors  of  the  ankle-joint.  Tibialis  posticus  and 
flexors  of  the  toes  rotate  the  foot  in.  The  three  peronei 
and  extensors  of  the  toes  rotate  outward. 

Peroneus  longus  strengthens  the  transverse  arch,  lifts 
the  outer  border  of  the  foot  in  walking,  extends  the 
foot,  depresses  the  first  metatarsal,  abducts  the  fore- 
foot, rotates  outward. 

Flexors  and  extensors  of  the  toes,  interossei,  and 
lumbricales  act  as  do  the  corresponding  muscles  of  the 
hand. 

Flexor  accessorius  modifies  the  action  of  the  flexor 
longus  digitorum,  as  those  tendons  cannot  enter  the 
foot  in  a  straight  line. 

The  extensor  brevis  digitorum  does  the  same  for  the 


172  MUSCLE  TISSUE 

extensor  communis,  though  here  they  are  not  so  much 
needed,  and  their  function  is  not  so  evident. 

Extensors  of  the  foot  slightly  rotate  inward ;  flexors  of 
the  foot  slightly  rotate  outward;  plaiitaris  indirectly 
pulls  up  the  capsule  of  the  ankle-joint  and  slightly  aids 
the  gastrocnemius. 

Flexors  of  the  foot.  Extensors  of  the  foot. 

Tibialis  anticus.  Tendo  Achillis. 

Extensor  communis  digitorum.       Peroneus  longus  and  brevis. 
Extensor  proprius  hallucis.  Tibialis  posticus. 

Peroneus  tertius.  Flexor    longus    digitorum     and 

hallucis. 

Adduction.  Abduction. 

Tibialis  posticus  (strongly).  Peroneus  brevis. 

Tendo  Achillis  (weakly) .  Peroneus  longus. 

Perhaps  tendons  behind  the 

inner    malleolus,    perhaps 

the  tibialis  anticus. 

Rotation  in.  Rotation  out. 

Tibialis  anticus  (strongly).  Peroneus  longus. 

Tendo  Achillis.  Extensor  communis  digitorum, 

Peroneus  tertius. 

The  Interosseous  Muscles. — hiterossei,  as  in  the  hand, 
are  seven  in  number,  four  dorsal  and  three  plantar. 
The  dorsal  project  downward  as  low  as  the  plantar, 
and  alternate  with  them.  Only  one  muscle  in  the 
first  space,  two  in  the  others.  The  second  phalanges 
are  their  centre  of  insertion. 


QUESTIONS 

1.  Name  the  three  varieties  of  muscle  tissue. 

2.  What  does  the  sarcoplasm  represent  in  muscle  tissue? 

3.  Does  the  sarcoplasm  possess  the  quality  of  contractility? 

4.  What  do  you  understand  by  a  skeletal  muscle? 

5    What  forms  the  fibers  in  a  muscle?     The  primary  bundles? 
Secondary? 

6.  What  is  the  function  of  the  epimysium?    Perimysium?    Endo- 
mysium? 

7.  Where  are  voluntary  striated  muscles  found  in  the  body? 
Involuntary  non-striated? 


MUSCLES  AND  FASCIA  OF  LOWER  EXTREMITY  173 

8.  Where  is  involuntary  striated  muscle  found? 

9.  What  influences  the  consistency  of  a  muscle? 

10.  What  effect  do  irritating  stimuli  have  upon  muscles? 

11.  What  stimulus  causes  muscle  to  contract  in  the  living  body? 

12.  Name  some  of  the  artificial  and  experimental  stimuli  for 
muscles. 

13.  What  is  the  function  of  a  tendon?    An  aponeurosis? 

14.  What  structure  of  bones  receives  the  attachment  of  muscles? 

15.  Give  the  names  applied  to  the  parts  of  a  muscle. 

16.  What  do  you  understand  by  the  origin  of  a  muscle?    Insertion? 

17.  Do  most  muscles  act  from  either  their  origin  or  insertion? 

18.  How  do  muscles  derive  their  names  in  the  living  body? 

19.  What  variety  of  tissue  forms  tendons?    Aponeuroses? 

20.  What  are  tendons  attached  to? 

21.  With  which  shaped  muscles  are  aponeuroses  usually  found? 

22.  Where  is  fascia  usually  found?. 

23.  In  the  description  of  a  muscle  what  must  be  included? 

24.  Name  the  muscles  of  mastication. 

25.  What  muscles  flex  the  forearm  upon  the  arm? 

26.  Give  action  of  the  latissimus  dorsi  muscle, 

27.  What  muscles  fill  up  the  intercostal  spaces  of  the  thorax? 

28.  Name  the  muscles  which  flex  the  fingers.    Extend. 

29.  What  muscles  form  the  thenar  eminence  of  the  hand?  Hypo- 
thenar? 

30.  Name  the  musculomembranous  structure  which  separates  the 
thorax  and  abdomen. 

31.  Give  the  origin  and  insertion  of  the  following  muscles:  Biceps 
(arm).  Sartorius.  Supinator  longus  or  brachioradialis.  Tibialis 
anticus.     Flexor  longus  hallucis.     Rectus  femoris.    Palmaris  longus. 

32.  Name  the  muscles  which  form  in  a  general  way  the  anterior 
abdominal  wall. 

33.  What  muscle  surrounds  the  eye  and  gives  it  function? 

34.  Name  the  muscles  which  adduct  the  thigh. 

35.  What  muscle  covers  the  shoulder-joint  on  its  outer  side? 

36.  Give  a  brief  description  of  the  scalp.  Of  the  fascia  of  the  palm 
of  the  hand. 


CHAPTER  VIII 

THE  DESCRIPTION  OF  THE  ANATOMY  AND 

PHYSIOJ.OGY  OF  THE  CIRCULATORY 

APPARATUS 

The  circulatory  apparatus  consists  of  the  heart, 
covered  by  the  pericardium,  the  arteries,  veins,  and 
capillaries,  and  circulating  fluid — the  blood. 


THE    PERICARDIUM 

The  pericardium  is  a  serofibrous  membrane  which 
invests  the  heart  and  the  great  vessels  at  their  origin 
for  about  two  inches.  The  pericardium  consists  of  a 
fibrous  and  serous  layer,  between  which  is  a  small 
amount  of  serous  fluid,  preventing  friction,  as  at 
each  rhythmic  contraction  of  the  heart  these  layers 
rub  against  each  other.  The  serous  layer  (epicar- 
dium)  invests  the  heart  muscle  and  is  reflected  to 
the  fibrous  layer. 

THE   HEART 

The  heart  is  a  hollow  muscular  organ  situated  in 
the  thorax  between  the  right  and  left  lobes  of  the 
lungs,  enclosed  by  the  pericardial  sac. 

It  lies  obliquely,  the  base  being  directed  upward, 
backward,  and  toward  the  right,  its  position  corre- 
sponding to  the  surface  of  the  chest  wall  extends 
from  the  fifth  to  the  eighth  thoracic  vertebra.  The 
apex  looks  downward,  forward,  and  to  the  left,  its 


THE  HEART  175 

impulse  against  the  chest  wall  being  felt  in  the  fifth 
interspace  on  the  left  side,  about  3|  inches  from  the 
middle  of  the  sternum.  The  posterior  or  postero- 
inferior  surface  is  flat,  formed  chiefly  by  the  wall  of 
the  left  ventricle,  and  rests  on  the  diaphragm;  its 
anterior  or  anterosuperior  surface  is  convex,  formed 
chiefly  by  the  wall  of  the  right  ventricle,  but  also 
partly  by  the  left,  and  is  overlapped  by  the  lungs, 
except  in  the  central  part.  The  borders  of  the  heart 
are  right  and  left,  the  former  is  long  and  thin,  the 
left  shorter  and  thicker.  The  length  of  the  heart  is 
about  5  inches,  the  greatest  breadth  3|  inches;  its 
thickness  about  2J  inches.  Its  weight  is  approxi- 
mately 10  to  12  ounces  in  the  male,  8  to  10  ounces  in 
the  female,  and  these  increase  with  age. 

Externally  its  surface  presents  a  deep  transverse 
groove,  auriculoventricular,  which  marks  an  upper 
auricular  and  lower  ventricular  portion;  this  latter 
part  presents  a  longitudinal  furrow  on  the  front  and 
the  back,  the  former  being  somewhat  to  the  left,  the 
latter  to  the  right,  marking  off  the  right  and  left 
ventricles  (interventricular  groove). 

The  heart  contains  four  chambers.  They  are  divided 
by  a  longitudinal  partition  or  septum  into  a  right  and 
left  part,  and  these  in  turn  are  subdivided  into  an 
auricle  and  a  ventricle  by  a  transverse  partition, 
which  is  perforated  on  each  side  by  an  opening,  called 
the  auriculoventricular,  connecting  the  auricle  and 
ventricle 

The  Cavities  of  the  Heart. — The  inner  surface  of 
the  heart  muscle  (myocardium)  is  lined  throughout 
by  a  thin  layer  of  membrane  called  the  endocardium. 
It  is  continuous  with  the  lining  membrane  of  the 
great  bloodvessels  opening  into  the  heart  cavities, 
and  helps  to  form  the,  various  valves  by  a  process,, 
whereby  the  membrane  is  thrown  into  folds.  The 
endocardium  consists  of  a  flattened  layer  of  endothelial 
cells  resting  on  a  membrane  formed  of  subendothelial 


176 


THE  CIRCULATORY  APPARATUS 


(fibro-elastic)    tissue.      On    opening    the    heart    the 
following  structures  can  be  seen  within  its  cavity: 

The  Right  Auricle. — This  is  larger  than  the  left,  its 
wall  being  about  one  line  in  thickness  and  its  capacity 
two  ounces.  Within  the  auricle  the  following  parts 
present  themselves  for  examination: 

Fia.  71 


Front  view  of  the  thorax,  showiug  relation  of  the  heart  and  its  valvea, 
lungs,  etc.,  to  the  ribs  and  sternum.  P,  pulmonary  orifice;  Ao,  aortic  orifice; 
M,  left  auriculoventricular  orifice;  Tr,  right  auriculoventricular  orifice. 


The  orifice  of  the  superior  vena  cava,  looking  downward 
and  forward.  The  orifice  of  the  inferior  vena  cava,  at 
the  lowest  part,   near  the  septum,   looking   upward 


THE  HEART 


177 


and  inward.  Between  the  two  caval  openings  a 
projection,  the  tubercle  of  Lower.  The  opening  of  the 
coronary  sinus,  between  the  inferior  cava  and  the 
auriculoventriciilar  opening,  and  protected  by  the  fold 
of  endocardium  forming  the  coronary  valve.     Numer- 

FiG.  72 


Foramina 
Thebcm 


Tubercle 
of  Lower. 


Bridle  passed  through 
ripht  auriniloveritHcular  opening. 

The  right  auricle  and  ventricle  laid  open,  the  anterior  walls  of  both  being 
removed.     (Gray.) 


ous  small  openings  {foramina  Thehesii)  of  the  small 
veins  of  the  heart.  The  auriculoventricular  opening, 
between  the  auricle  and  ventricle.  The  Eustachian 
valve,  between  the  front  of  the  inferior  vena  cava 
12 


178  THE  CIRCULATORY  APPARATUS 

and  the  auriculoventricular  orifice.  It  is  semilunar 
in  form,  the  free  concave  margin  sending  one  cornu 
to  join  the  front  of  the  annulus  ovahs  and  the  other  to 
the  auricular  wall.  The  fossa  ovalis,  at  the  back  of  the 
septum,  in  the  situation  of  the  fetal  foramen  ovale, 
its  prominent  margin  being  known  as  the  annulus 
ovalis.  The  musculi  pectmati,  small  elevated  columns 
which  traverse  the  appendix  and  the  adjacent  part 
of  the  sinus. 

The  Right  Ventricle. — ^This  is  pyramidal,  and  extends 
nearly  to  the  apex  of  the  heart.  It  is  bounded  inter- 
nally by  the  convex  surface  of  the  wall  of  the  ven- 
tricles, and  prolonged  above  and  internally  into  a 
pouch,  the  infundibulum,  or  conus  arteriosus,  from 
which  springs  the  pulmonary  artery.  Its  cavity  has 
a  capacity  of  three  ounces.  On  opening  the  ventricle 
the  following  parts  are  presented  for  examination: 

The  auriculoventricular  orifice^  oval  in  form,  and 
placed  near  the  right  side  of  the  heart.  Around  its 
circumference  is  a  fibrous  ring,  and  it  is  guarded  by 
the  tricuspid  valve.  The  opening  of  the  pulmonary 
artery,  circular  in  form,  at  the  summit  of  the  conus 
arteriosus,  near  the  septum;  is  guarded  by  the  pul- 
monary valves  (semilunar) .  The  tricuspid  valve  consists 
of  three  triangular  flaps  formed  of  fibrous  tissue  covered 
by  endocardium.  They  are  continuous  with  one 
another  at  their  bases,  and  their  free  margins  and 
ventricular  surfaces  give  attachment  to  the  chordae 
tendinese.  Their  central  part  is  thick  and  strong,  the 
lateral  margins  thinner  and  flexible.  The  chordce 
tendineoB  are  attached  as  follows:  several  to  the  attached 
margin  of  each  flap,  blending  with  the  fibrous  ring; 
several  to  the  strong  central  part;  and  the  finest  and 
most  numerous  to  the  margins  of  each  curtain.  The 
columnce  carneoe  are  projecting  bundles  of  muscular 
substance  found  all  over  the  ventricular  wall  excepting 
the  conus  arteriosus.  They  afford  attachment  for 
the   papillary   muscles.     The   three   semilunar  valves 


THE  HEART  179 

guard  the  pulmonary  orifice.  They  are  semicircular, 
their  free  margins  being  thick  and  tendinous,  and 
presenting  at  the  middle  a  small  fibrous  nodule,  the 
corpus  Arantii.  On  each  side  of  this  body,  just  behind 
the  free  margin,  the  valve  presents  a  small  thinned- 
out  interval,  and  when  the  valves  are  closed 
during  diastole  these  valves  are  in  contact,  and  so 
also  are  the  three  nodules.  These  latter  prevent 
any  leakage  from  the  triangular  space  which  would 
otherwise  be  left.  At  the  commencement  of  the 
pulmonary  artery  are  three  pouches,  the  sinuses  of 
Valsalva,  placed  one  behind  each  valve.  They  resemble 
those  of  the  aorta,  but  are  smaller. 

The  Left  Auricle. — This  is  smaller  and  thicker  walled 
than  the  right,  and  consists,  like  the  right,  of  a  sinus 
and  an  appendix.  The  latter  overlaps  the  pulmonary 
artery.  Within  it  presents  the  following  features 
of  interest: 

The  orifices  of  the  pulmonary  veins,  opening  two 
into  the  right  and  two  into  the  left  side  (sometimes 
only  three  are  seen);  the  auriculoventricular  orifice; 
and  a  few  musculi  pectinati  on  the  inner  side  of  the 
appendix. 

The  Left  Ventricle. — This  is  longer  than  the  right,  and 
forms  the  apex  of  the  heart.  Its  walls  are  three  times 
as  thick  as  those  of  the  right.  Within  it  presents  for 
examination : 

The  auriculoventricular  orifice,  which  is  smaller  than 
the  right  and  guarded  by  the  mitral  or  bicuspid 
valve;  and  the  aortic  opening,  in  front  and  to  the 
right  of  the  preceding,  guarded  by  the  semilunar 
valves.  The  mitral  valve  is  attached,  like  the  tricuspid, 
on  the  right  side.  It  consists  of  two  curtains  which 
are  larger  and  thicker  than  those  of  the  tricuspid, 
and  of  two  smaller  segments,  one  at  each  angle  of 
junction  of  the  former.  They  are  furnished  with 
chordae  tendinese.  The  aortic  semilunar  valves  are 
similar  to  but  larger  and  stronger  than  the  pulmonary 


180  THE  CIRCULATORY  APPARATUS 

valves.  ColumncB  carnece  are  found  in  the  right 
ventricle,  and  the  musculi  papillares  are  very  large; 
one  is  attached  to  the  anterior  wall,  the  other  to  the 
posterior. 

See  Fig.  71  for  relation  of  the  valves  and  orifices  of 
the  heart  to  the  chest  wall. 

The  muscle  fibers  of  the  heart  are  attached  to  car- 
tilaginous rings  which  surround  the  auriculoventricular 
and  arterial  orifices. 

Nerves.— (See  pages  121,  383.) 

THE   CIRCULATION   OF   THE   BLOOD 

The  heart  is  the  pump  which  propels  the  blood, 
aided  by  the  elasticity  of  the  arteries,  veins,  and 
connecting  capillaries  throughout  the  body.  Without 
the  rhythmical  contraction  of  the  heart  muscle,  life 
cannot  be  maintained.  The  blood  courses  through 
the  cavities  of  the  heart  as  follows.  Allowing  that 
the  heart  has  emptied  its  chambers,  this  blood  is 
returned  to  the  heart  as  venous  blood  through  the 
superior  and  inferior  vena  cavae  which  open  into  the 
right  auricle,  from  which  it  passes  to  the  right  ven- 
tricle through  the  auriculoventricular  opening.  The 
blood  now  is  forced  into  the  pulmonary  artery  and 
its  branches  to  the  pulmonary  capillaries  in  the  lungs, 
where  the  blood,  coming  in  contact  with  the  air  we 
breathe,  by  a  process  of  gaseous  exchange,  gives  up 
the  carbon  dioxide  to  the  lungs,  and  absorbs  oxygen, 
becoming  bluish  red  or  scarlet  in  color.  This  new  or 
arterialized  blood  is  carried  back  by  the  pulmonary 
veins  to  the  left  auricle  of  the  heart,  flows  through  the 
left  auriculoventricular  opening  into  the  left  ventricle 
and  thence  through  the  aorta  to  the  small  arteries 
coursing  along  until  the  capillaries  are  reached  in 
every  part  of  the  body,  when  by  the  same  gaseous 
exchange  as  we  said  occurred  in  the  lungs,  the  blood 
gives  up  its  oxygen  to  the  tissues  and  absorbs  the 


PLATE    III 


Pulm  on  a  ry  Capillaries 


Diagram  to  Show  liie  Course  of  the  Circulation 
of  the   Blood. 

This  diagram  does  not  show  that  the  liver  also  receives   blood 
through  the  hepatic  artery. 


THE  CIRCULATION  OF  THE  BLOOD  181 

carbon  dioxide  from  them,  and  is  changed  from  a 
scarlet  to  a  bluish  red  color.  The  same  venous  return 
of  the  blood  occurs  to  the  right  auricle  and  the  cycle 
is  repeated.  It  must  be  remembered  that  while  the 
vense  cavae  are  filling  the  right  auricle,  the  pulmonary 
veins  are  at  the  same  instant  pouring  their  contents 
into  the  left  auricle. 

The  blood  is  moved  through  the  heart  and  blood- 
vessels by  a  continuous,  rhythmic,  and  automatic 
contraction  and  relaxation  of  the  heart  muscle  due 
to  an  inherent  power  possessed  by  the  heart  of  con- 
verting potential  energy  stored  up  during  the  period 
of  rest  into  kinetic  energy,  i.  e.,-  heat  and  mechanic 
motion.  The  rhythmic  contraction  wave  of  the 
heart  is  carried  on  by  means  of  a  thin  and  distinct 
bundle  of  muscle  fibers — the  bundle  of  His  or  atrioven- 
tricular. It  commences  in  the  right  auricle  near  the 
orifice  of  the  Eustachian  valve  and  passes  to  the  wall 
between  the  ventricles  to  end  in  the  papillary  muscles 
of  the  ventricles.  Disease  or  injury  to  these  fibers 
causes  an  interference  with  the  muscular  contraction 
which  begins  in  the  auricle  and  extends  to  the  ventricles. 
This  leads  to  a  condition  which  arises  as  a  result  of  the 
auricle  continuing  to  contract,  and  forces  the  blood  into 
the  ventricles,  allowing  the  blood  to  be  continuously 
pumped,  while  the  ventricle  not  responding  permits  the 
blood  to  collect,  due  to  its  inability  to  contract.  This 
condition  is  called  Adams- Stokes  sign  or  heart-block  and 
is  fatal.  When  any  portion  of  the  heart  contracts  it 
is  called  the  systole,  and  relaxation,  the  diastole.  The 
heart  having  two  cavities  on  each  side,  when  their 
walls  contract  and  relax  in  succession  we  speak  of 
an  auricular  systole  and  diastole,  and  a  ventricular 
systole  and  diastole. 

The  contraction  systole  of  the  heart  muscle  starts 
as  a  wave  in  the  great  veins  and  then  passes  to  the 
base  of  the  heart  in  both  auricles,  and  extends  rapidly 
over  the  ventricles  to  the  apex;  during  this  period 


182'  THE  CIRCULATORY  APPARATUS 

the  auricles  and  ventricles  empty  their  cavities  of 
blood  into  the  pulmonary  and  arterial  systems  from 
the  right  and  left  sides  of  the  heart  respectively. 
Following  this  contraction  wave  is  a  pause  or  relaxa- 
tion of  the  muscle — the  diastole — during  which  time 
the  blood  rapidly  flows  into  the  auricles  and  ven- 
tricles, and  at  the  end  of  the  relaxation  or  diastole 
there  is  a  period  of  rest,  during  which  time  the  auricles 
and  ventricles,  or,  in  fact,  the  whole  heart,  is  quietly 
filling  with  more  blood,  when  the  phenomenon  is 
resumed. 

The  Part  Played  by  the  Heart  Muscle  and  Valves 
during  the  Course  of  the  Blood  through  the  Chambers 
of  the  Heart. — ^We  will  start  by  allowing  that  the 
contraction  or  systole  of  the  ventricle  has  occurred. 
Instantly  the  column  of  blood  forced  into  the  aorta 
and  pulmonary  artery,  by  filling  the  sinuses  of  Val- 
salva, forces  the  margins  of  the  semilunar  valves 
together  and  prevents  the  return  of  the  blood  to  the 
ventricles  from  the  aorta  and  pulmonary  artery; 
while  the  ventricle  contraction  or  systole  was  emptying 
its  chambers,  the  auricles  were  filling  from  the  venae 
cavse  and  pulmonary  veins,  and  this  blood  was  rapidly 
passed  into  the  ventricles  during  the  relaxation  or 
diastole,  while  a  new  supply  has  taken  its  place  in 
the  auricles,  the  ventricles  becoming  distended  with 
more  blood  (during  the  period  of  rest)  force  upward 
the  tricuspid  and  mitral  valves,  gradually  closing  the 
auriculoventricular  openings.  Suddenly  the  auricles 
contract  or  begin  their  systole,  and  more  blood  is 
forced  into  the  ventricles,  the  valves  close;  immedi- 
ately the  ventricular  systole  or  contraction  takes 
place,  thQ  blood  not  being  able  to  pass  back  into  the 
auricles  owing  to  the  closure  of  the  auriculoventricular 
openings,  is  forced  into  the  aorta  and  pulmonary 
artery,  when  the  semilunar  valves  are  flattened  against 
the  walls  by  the  pressure  from  the  blood  in  the  ven- 
tricles.   Now  the  ventricular  systole  is  completed,  the 


THE  CIRCULATION  OF  THE  BLOOD  183 

semilunar  valves  are  instantly  closed  to  prevent  a 
return  of  blood  to  the  ventricles  from  the  aorta  and 
pulmonary  artery;  the  period  of  rest  occurs,  following 
the  emptying  of  the  ventricles,  and  the  cycle  is  repeated. 
The  Cardiac  Cycle  or  Revolution. — This  has  been 
shown  above  to  consist  of  (1)  an  auricular  contraction, 
(2)  ventricular  contraction,  (3)  the  period  of  repose, 
during  which  time  the  auricles  and  ventricles  are  at 
rest.  There  are  72  cycles  per  minute  made  by  the 
heart  of  a  healthy  adult,  and  the  average  duration  of 
each  cycle  is  about  eight-tenths  of  a  second,  divided 
as  follows: 

Auricular  systole  yV  Auricular  diastole  yV 

Ventricular  systole  to  Ventricular  diastole  y^ 

Common  pause  yj 

The  Heart-beats. — In  a  healthy  adult  the  pulsations 
or  cardiac  cycles  are  72  per  minute;  in  the  fetus,  140  per 
minute;  during  the  first  year  of  life  it  decreases  to 
128  per  minute;  during  the  third  year  to  95  per  minute; 
from  the  eighth  to  the  fourteenth  year,  84  per  minute. 
It  is  more  rapid  in  the  female,  averaging  8  to  10 
more  beats  per  minute.  The  pulse  of  a  person  lying 
down  is  a  few  beats  less  than  when  sitting  or  stand- 
ing. Exercise  and  digestion  temporarily  increase  the 
number  of  beats. 

The  Heart  Sounds. — On  placing  the  ear  or  the 
stethoscope  to  the  chest  wall  overlying  the  heart,  or 
in  the  fifth  intercostal  space,  3i  inches  from  the 
middle  of  the  sternum,  two  sounds  resembling  the 
pronouncing  of  the  syllables  lubb-dupp,  lubb-dupp, 
will  be  heard.  They  accompany  each  pulsation  of 
the  heart  and  are  called  the  first  and  second  sounds; 
the  former  is  dull  and  long,  and  occurs  with  the 
cardiac  systole  or  contraction;  the  latter  is  short  and 
clear  and  occurs  at  the  commencement  of  diastole  or 
relaxation  of  the  heart  muscle.  The  cause  of  the 
first  sound  is  supposed  to  be  due  to  the  contraction  of 


184  THE  CIRCULATORY  APPARATUS 

the  muscular  walls  of  the  ventricles,  the  gradual 
closure  and  vibrations  of  the  mitral  and  tricuspid 
valves,  and  the  sudden  pressure  of  the  apex  against 
the  chest  wall.  The  second  sound  is  supposed  to  be 
due  to  the  sudden  closure  and  vibrations  of  the  semi- 
lunar valves  in  the  aorta  and  pulmonary  artery, 
following  the  ventricular  systole  or  contraction;  also 
the  sound  is  added  to  by  the  whirling  of  the  column 
of  blood  against  those  closed  valves  at  the  beginning 
of  diastole  or  relaxation  of  the  ventricles. 

The  Fetal  Circulation. — The  fetus  is  nourished  by 
the  blood  from  the  placenta  (afterbirth).  The  blood 
is  conveyed  from  the  placenta  to  the  fetus  by  the 
umbilical  vein.  This  vein  enters  the  umbilicus  and 
passes  upward  along  the  upper  free  margin  of  the 
suspensory  ligament  of  the  liver  to  the  under  surface 
of  the  liver.  The  blood  after  nourishing  the  organ 
by  two  or  three  branches,  finally  reaches  the  inferior 
vena  cava  by  way  of  the  hepatic  veins,  and  the  ductus 
venosus,  which  runs  from  ^  the  transverse  fissure  of 
the  liver  to  open  into  the  hepatic  veins  just  before 
they  open  into  the  inferior  vena  cava.  The  superior 
and  inferior  vena  cava  open  into  the  right  auricle  of 
the  heart. 

The  course  of  the  blood  through  the  chambers  of 
the  fetal  heart  differs  from  that  observed  in  the  adult, 
viz.,  the  blood  from  the  inferior  cava  passes  into  the 
right  auricle  and  then  is  directed  by  the  Eustachian 
valve  to  the  left  auricle  of  the  heart  through  the 
foramen  ovale.  In  the  left  auricle  the  blood  from  the 
right  auricle  becomes  mixed  with  a  small  quantity 
of  blood  returned  from  the  lungs  by  the  pulmonary 
veins.  This  blood  then  passes  into  the  left  ventricle 
(as  seen  in  the  adult)  and  then  into  the  aorta,  by  which 
vessel  it  is  distributed  almost  entirely  to  the  head  and 
upper  extremities.  The  blood  is  returned  from  the 
head  and  upper  extremities  by  the  veins,  which 
ultimately  drain  into  the  superior  vena  cava,  that 


Ductus  arteriosus 


Plan  of  the  Fetal  Circulation. 


In    this    plan  the    figured    arrows    represent   the   kind    of   blood,  as 
well    as   the    direction    which    it    takes  in    the    vessels.      Thus,  arterial 

blood    is    figured    >> — — >  ;      venous    blood,    >> >;    mixed 

(arterial  and   venous)    blood,  >> >. 


THE  CIRCULATION  OF  THE  BLOOD  185 

opens  into  the  right  auricle  of  the  heart.  From  the 
right  auricle  the  blood  passes  over  the  Eustachian 
valve  into  the  right  ventricle,  then  from  the  latter 
into  the  pulmonary  artery.  The  lungs  of  the  fetus 
being  inactive,  require  only  enough  blood  to  develop 
and  nourish  them,  this  quantity  of  blood  is  conveyed 
by  the  pulmonary  arteries  and  returned  to  the  pul- 
monary veins  to  the  left  auricle;  the  greater  quantity 
of  blood  from  the  right  ventricle  passes  through  the 
ductus  arteriosus  (a  small  vessel  connecting  the  pul- 
monary artery  with  the  aorta)  into  the  beginning  of 
the  descending  aorta,  where  it  becomes  mixed  with 
the  blood  from  the  left  ventricle. 

The  general  distribution  of  blood  through  the  body 
of  the  fetus  is  similar  to  the  adult  system,  with  the 
exception  of  the  above-mentioned  differences  and  the 
return  of  waste  materials  from  the  fetus  to  the  placenta 
by  way  of  the  hypogastric  arteries,  which  are  branches 
of  the  internal  iliacs  and  join  the  umbilical  vein  at 
the  umbilicus  (navel)  to  assist  in  forming  the  umbilical 
cord  of  the  fetus. 

The  Changes  in  the  Circulatory  Apparatus  following 
Birth. — With  the  commencement  of  normal  respiration 
(the  umbilical  cord  being  ligated),  the  placental  circu- 
lation is  cut  off.  Anywhere  within  ten  days  after 
birth  the  foramen  ovale  closes  and  may  continue  as 
a  slight  opening  and  not  be  injurious  to  health  until 
the  final  closure.  When  the  foramen  does  not  close, 
the  skin,  etc.,  becomes  cyanotic,  due  to  the  mixing  of 
the  arterial  and  venous  blood — the  so-called  blue  baby. 

The  umbilical  vein,  ductus  venosus,  and  arteriosus 
atrophy,  and  also  the  hypogastric  arteries.  Thus  the 
infant  vascular  apparatus  assumes  the  normal  course 
as  described  in  the  adult. 

Structure  and  Functions  of  the  Arteries,  Veins,  and 
Capillaries. — The  Arteries.— These  are  closed  tubes 
which  convey  the  blood  and  keep  it  in  circulation 
from  the  heart  cavities  throughout  the  body. 


186  THE  CIRCULATORY  APPARATUS 

The  typical  artery  consists  of  three  coats:  internal 
or  tunica  intima;  middle  or  tunica  media;  an  external 
or  tunica  adventitia.  Aside  from  the  latter,  most 
arteries  are  covered  by  a  sheath  of  connective  tissue 
derived  from  the  fascia  of  the  part  of  the  body  in 
which  they  are  found,  and  held  to  the  artery  by 
fibrous  tissue. 

Fig.  73 


Transverse  section  of  part  of  the  wall  of  the  posterior  tibial  artery.  X  75. 
A',  endothelial  and  subendothelial  layers  of  inner  coat.  B,  elastic  layer  (fenes- 
trated membrane)  of  inner  coat,  appearing  as  a  bright  line  in  section.  C, 
muscle  layer  (middle  coat).  D.  outer  coat,  consisting  of  connective-tissue 
bundles.  In  the  interstices  of  the  bundles  are  some  connective- tissue  nuclei, 
and,  especially  near  the  muscular  coat,  a  number  of  elastic  fibers  cut  across, 
(Schafer.) 

The  muscular  tissue  (media)  is  not  so  well-marked  in 
the  larger  arteries,  but  the  elastic  tissue  predominates 
and  is  more  closely  arranged;  in  the  smaller  arteries 
the  elastic  tissue  is  in  excess,  while  only  a  single 
layer  of  muscle  tissue  is  present;  the  larger  arteries 
possess  a  thicker  outer  or  fibrous  coat  than  the  smaller 
vessels. 

All  arteries  possess  elasticity  and  contractility  due 
to  the  presence  in  their  walls  of  the  elastic  (intima) 
and  muscle  (media)  coats. 

Elasticity. — This  elastic  property  possessed  by 
arteries  permits  their  wall  to  expand  and  recoil  to 
adapt  itself  to  the  pressure  and  reaction  of  the  column 
of  blood  thrown  into  the  arterial  system  from  the 
ventricle  of  the  heart  at  each  contraction  or  systole 
and  subsequent  relaxation  or  diastole. 


THE  CIRCULATION  OF  THE  BLOOD  187 

This  elasticity  of  the  arterial  wall,  in  response  to 
the  pressure  and  reaction  of  the  column  of  blood 
imparted  to  it  by  the  heart  muscle,  develops  into  a 
remittent  expansion  and  recoil  of  the  arterial  wall, 
which  becomes  fainter  the  more  distant  the  vessels 
are  from  the  heart.  When  the  capillaries  are  reached 
it  is  a  continuous  or  a  steady  flow  of  blood,  without 
any  recoil  of  the  arterial  wall,  which  passes  into  the 
veins.  Thus  the  elasticity  of  the  arteries  is  for  the 
purpose  of  equalizing  the  movement  of  the  blood 
throughout  the  arterial  system. 

Contractility. — Contractility  of  the  arteries  is  depen- 
dent upon  the  muscular  tissue  in  their  walls.  They 
are  supplied  by  nerve  filaments  which  receive  impulses 
from  the  controlling  centres  in  the  spinal  cord,  which 
communicate  by  means  of  ganglia  with  the  sympathetic 
system,  and  the  latter  distributes  filaments  to  the 
middle  or  muscular  coat  of  the  arteries.  The  centres 
in  the  spinal  cord  are  called  the  vasomotor  centres,  and 
the  nerve  filaments  the  vasomotor  nerves.  The  centres 
in  the  spinal  cord  are  influenced  chiefly  by  a  main 
centre  situated  in  the  medulla;  in  other  words,  the 
spinal  centres  are  underlying  centres  of  this  system. 

The  vasomotor  nerves  possess  two  sets  of  fibers: 
those  which  when  stimulated  raise  the  blood  pressure 
or  contract  the  arterial  wall — called  vasoconstrictor 
nerves;  and  those  w^hich  lower  arterial  pressure  or 
dilate  the  arterial  wall — called  vasodilator  nerves. 
These  two  sets  of  nerves,  both  when  active  although 
antagonistic  to  each  other  in  function,  tend  to  keep 
the  arteries  in  a  normal  state  of  contraction,  thus 
regulating  the  blood  pressure  and  caliber  of  the 
arteries. 

The  vasa  vasorum  is  the  term  defining  the  blood- 
vessels which  supply  the  walls  of  the  arteries.  They  are, 
of  course,  very  minute  bloodvessels  which  nourish 
them,  and  are  derived  from  adjacent  branches  and  have 
no  direct  opening  into  the  channel  of  the  artery  they 


188 


THE  CIRCULATORY  APPARATUS 


Fio.  74 


supply.  They  are  located  in  the  tunica  media  or 
middle  coat.  The  lining  coat  or  intima  of  an  artery 
is  nourished  by  the  column  of  blood  passing  over  it. 

The  arteries  give  off  branches  which  become  smaller 
as  their  destination  —  the  capillary  area   of  the  cir- 
culation— is   reached.     Just   before 
emerging  into  capillaries,  these  small 
branches  are  termed  arterioles. 

The  Capillaries. — The  capillaries 
consist  of  a  series  of  minute  blood- 
vessels which  divide  and  subdivide 
to  form  interlacing  net-works.  The 
walls  of  a  capillary  consist  of  a  single 
layer  of  flattened  endothelial  cells, 
nucleated,  and  held  together  by  a 
cement  substance.  These  thin-walled 
vessels  possess  irritability,  contrac- 
tility, and  tonicity.  They  freely 
communicate  with  one  another,  and 
are  the  connecting  link  for  the  pas- 
sage of  the  blood  from  the  arteries 
to  the  veins.  They  are  just  large 
enough  to  transmit  a  small  red  cell. 
The  functions  of  the  capillary  wall 
is  to  allow  an  exchange  of  the  nutri- 
tive elements  of  the  blood  with  the 
tissues,  and  to  receive  from  the  tissue 
the  waste  products  arising  as  a  result 
of  metabolism,  taking  place  in  the 
protoplasm  of  the  tissue  cells.  This 
interchange  between  the  blood  and  the  tissues  is 
due  to  the  thinness  of  the  capillary  wall,  aided  by 
the  phenomena  of  diffusion,  osmosis,  and  infiltration 
(see  Absorption,  page  286). 

The  Veins. — The  veins  consist  of  three  coats:  the 
tunica  intima,  media,  and  adventitia.  They  differ 
from  the  arteries  by  their  middle  coat  possessing 
less  elastic  and  muscular  tissue,  but  an  increase  in  the 


Capillaries  from  the 
mesentery  of  a  guinea- 
pig  after  treatment  with 
a  solution  of  nitrate  of 
silver:  a,  cells;  b,  their 
nuclei.     (Gray.) 


THE  CIRCULATION  OF  THE  BLOOD  189 

amount  of  fibrous  connective  tissue.  They  readily 
collapse  when  empty,  do  not  pulsate,  and  possess 
elasticity  and  contractility,  but  not  as  marked  as 
seen  in  the  arteries;  however,  these  properties  aid  in 
forcing  the  column  of  blood  toward  the  heart,  after 
leaving  the  capillaries — particularly  after  any  obstruc- 
tion to  the  flow  of  the  blood  stream.  The  veins  collect 
the  blood  from  the  capillary  area  throughout  the 
body,  and  return  it  to  the  right  side  of  the  heart. 
They  start  as  very  small  vessels — called  venules,  and 
then  become  veins,  which  increase  in  size  as  they 
course  toward  their  main  trunks. 

Veins  possess  valves,  arranged  in  pairs,  composed 
of  folds  of  the  lining  membrane  intima.  They  always 
project  toward  the  heart,  and  are  flattened  against  the 
wall  of  the  vessel  if  the  blood  is  flowing  unobstructed 
toward  the  heart;  but  when  any  obstruction  takes 
place  they  are  distended  into  the  channel,  preventing 
a  return  flow,  or  regurgitation  of  the  blood. 

The  veins  distend  under  these  conditions — due  to 
their  elasticity  and  accommodate  the  blood,  until  the 
obstruction  is  removed,  when  the  muscle  fibers  in 
the  wall  contract  and  force  the  column  of  blood 
onward.  With  the  congestion  relieved,  the  valves 
again  collapse  against  their  walls. 

The  Pulse. — ^The  pulse  is  the  regular  beat  which 
is  transmitted  to  the  examining  finger  when  placed 
on  an  artery.  It  is  felt  best  in  the  radial  artery  by 
making  gentle  pressure  with  the  tip  of  the  index 
finger  in  the  region  of  the  artery  at  the  lower  fourth 
of  the  forearm  on  the  outer  side — ^when  the  palm 
is  turned  upward  or  supinated,  just  a  little  above 
and  to  the  inner  side  of  the  prominence  of  the 
styloid  process  of  the  radius.  By  pressing  downward 
the  beat  or  pulsation  can  be  felt.  The  artery  lies 
on  a  firm  bed  formed  by  the  flexor  longus  pollicis, 
and  pronator  quadratus  muscles,  beneath  which  is 
the  bone.    The  expansion  of  the  artery  is  due  to  the 


190  THE  CIRCULATORY  APPARATUS 

response  of  the  arterial  system — which  is  receiving 
at  every  systole  or  contraction  of  the  ventricle — a 
large  volume  of  blood;  the  shrinkage  of  the  artery  is 
due  to  the  elastic  recoil  of  the  arterial  system  or  their 
walls  upon  the  volume  of  blood,  forcing  it  forward, 
into,  and  through  the  arteries,  during  the  diastole 
or  relaxation  of  the  ventricles.  The  pulse  or  pulse 
wave  is  simply  a  wave  passing  from  the  heart  over 
the  arterial  system,  forcing  the  blood  throughout  the 
body  until  the  capillaries  are  finally  reached,  when 
the  column  of  blood  passes  into  the  venous  system. 

The  number  of  beats  of  the  pulse  is  72  per  minute, 
and  varies  accordingly.  (See  Heart-beat,  page  183.) 
The  pulse  is  influenced  by  the  same  factors  which  inter- 
fere with  the  heart's  action.  The  pulse  is  spoken  of 
as  frequent  or  infrequent,  depending  w^hether  it  is 
above  or  below  the  normal  rate — 72  per  minute; 
quick  or  slow  according  to  the  suddenness  w^ith  which 
it  strikes  the  examining  finger;  hard  or  soft,  tense  or 
easily  compressible,  depending  on  the  resistance  which 
the  artery  offers  to  the  compressing  finger;  large,  full, 
or  small,  depending  on  the  amount  of  blood  in  the 
arterial  system  at  the  time  of  examination. 

The  Blood-pressure. — The  blood-pressure  or  arterial 
tension  may  be  defined  as  the  pressure  exerted  radially 
or  laterally  by  the  moving  blood-stream  against  the 
sides  of  the  vessels  (Brubaker). 

The  blood -pressure  is  greatest  in  the  aorta  and 
gradually  lessens  as  the  blood  is  forced  through  the 
vessels  and  emerges  into  the  arterioles  and  capillaries, 
then  passes  through  the  venules  into  the  veins. 

At  each  contraction  of  the  heart  a  large  volume  of 
blood  is  thrown  into  the  arterial  system,  which  is 
already  engorged.  This  mass  of  blood  in  the  arterioles 
and  capillaries  must  be  forced  along  to  accommodate 
the  next  column  of  blood  thrown  from  the  ventricle, 
to  relieve  the  arterial  system  of  its  already  over- 
distended  condition,  and  maintains  an  even  distribution 


DESCRIPTION  OF  THE  ARTERIES  191 

of  blood  through  the  vascular  system.  Owing  to  the 
small  caliber  of  the  arterioles  the  blood  meets  with 
considerable  resistance  in  passing  through  the  arterioles. 
As  a  result,  there  is  a  marked  decrease  in  the  pressure 
in  the  arterioles  and  capillaries,  due  to  this  great 
resistance,  which  is  called  the  peripheral  resistance. 
The  latter  is  caused  by  the  small  diameter  of  the 
vessels  modified  by  the  tonic  contraction  of  the 
muscles  in  the  wall  of  the  arterioles. 

A  practical  idea  of  the  blood-pressure  can  be  obtained 
from  observing  a  cut  or  injured  bloodvessel.  If  a 
large  artery,  the  blood  will  be  seen  to  project  from 
the  cut  end  nearest  the  heart,  as  a  bright  red  fluid 
spurting  from  the  vessel,  with  considerable  force, 
dependent  on  the  degree  of  pressure  which  it  had 
been  subjected  to  in  the  vessel,  and  the  tension  of 
the  vessel  wall  before  the  injury.  A  vein  when  injured 
bleeds  with  no  spurting  or  force.  It  is  seen  as  a  dark 
blue  fluid  coming  from  the  cut  end  away  from  the 
heart,  as  a  steady  stream  (welling  up).  These  differ- 
ences in  the  characters  of  the  hemorrhage  from  an  arte- 
rial and  venous  course  indicate  the  difference  of  blood- 
pressure  between  the  arterial  and  venous  systems. 

The  venous  pressure  continues  to  fall  from  the 
capillaries  to  the  heart.  There  is  simply  a  steady 
tone  to  the  walls  of  the  veins  which  propel  the  blood 
to  the  right  side  of  the  heart  without  any  pulsation. 

The  capillary  pressure  is  dependent  on  the  blood- 
pressure  of  the  arterioles  and  venous  systems.  It 
is  too  minute  to  observe  under  normal  physiological 
conditions. 

THE  DESCRIPTION  OF  THE  ARTERIES,  THEIR 
DISTRIBUTION,  ETC. 

There  are  two  great  arterial  systems:  (1)  The 
pulmonary,  to  the  lungs;  (2)  the  corporeal,  to  every 
other  part  of  the  body. 


192  THE  CIRCULATORY  APPARATUS 

The  Pulmonary  Arterial  System. — The  pulmonary 
artery  is  a  short,  wide  vessel,  2  inches  in  length.  Com- 
mencing at  the  base  of  the  right  ventricle,  it  curves 
upward  and  backward,  to  end  under  the  transverse 
aorta  by  dividing  into  a  right  and  a  left  branch,  which 
convey  the  blood  from  the  right  auricle  to  the  lungs. 

This  vessel,  with  the  ascending  aorta,  is  enclosed  in  a 
sheath  of  pericardium.  It  winds  around  the  aorta, 
being  at  first  in  front,  and  later  to  the  left  side,  of  the 
ascending  portion.  In  fetal  life  the  ductus  arteriosus 
connects  it  a  little  to  the  left  of  its  division  with  the 
transverse  aorta. 

Each  branch  enters  the  hilum  of  the  corresponding 
lung;  the  right,  the  larger,  passing  behind  the  ascending 
aorta  and  superior  vena  cava;  the  left,  in  front  of  the 
descending  aorta.  The  left  divides  into  two  branches 
for  the  lobes  of  the  left  lung;  the  right  also  divides 
into  two  primary  branches  for  the  upper  and  lower 
lobes.  From  the  lower  one  of  these  is  sent  a  branch 
to  the  middle  lobe.  The  pulmonary  arteries  are  the 
only  arteries  which  carry  venous  blood. 

The  Corporeal  Arterial  System.  —  The  Aorta. — 
The  aorta  is  the  main  trunk  from  which  spring  the 
systemic  arteries.  From  the  base  of  the  left  ventricle 
it  runs  upward,  forward,  and  to  the  right  as  far  as 
the  second  right  cartilage;  then  backward  and  to  the 
left,  over  the  root  of  the  left  lung,  to  the  fourth  dorsal 
vertebra;  thence,  along  the  spine,  it  descends  through 
the  thorax  and  abdomen,  to  divide  at  the  fourth 
lumbar,  into  the  common  iliacs. 

It  has  been  divided,  for  convenience  of  description, 
into  the  arch  and  the  descending  aorta.  The  arch  is 
subdivided  into  the  ascending,  transverse,  and  descend- 
ing parts;  the  descending  aorta,  into  the  thoracic  and 
abdominal  portions. 

The  Arch  of  the  Aorta.  The  ascending  part  of 
the  arch  runs  upward,  forward,  and  to  the  right,  from 
a  point  opposite  the  lower  border  of  the  third  left 


DESCRIPTION  OF  THE  ARTERIES  193 

Fia.  75 


Becnrren 


The  arch  of  the  aoita  and  its  branches.     (Gray.) 


13 


194  THE  CIRCULATORY  APPARATUS 

cartilage,  to  the  upper  border  of  the  second  right 
cartilage.  Close  to  its  origin  it  presents  three  small 
dilatations,  the  sinuses  of  Valsalva,  indicating  the 
situation  of  the  semilunar  valves. 

The  transverse  part  of  the  arch  passes  backward  and 
to  the  left  as  far  as  the  left  side  of  the  body  of  the 
fourth  dorsal  vertebra. 

The  descending  part  of  the  arch  descends  to  the 
lower  border  of  the  fifth  dorsal  vertebra,  ending  in 
the  thoracic  aorta. 

The  Branches  of  the  Arch  of  the  Aorta. — The 
branches  of  the  arch  are  five — coronary,  right  and 
left,  from  the  ascending  part;  and  the  innominate, 
left  carotid,  and  left  subclavian,  from  the  transverse 
part.    The  descending  part  gives  oft'  no  branches. 

The  coronary  arteries  supply  the  heart  and  the  coats 
of  the  great  vessels. 

The  innominate  (brachiocephalic)  artery  is  the  largest 
branch.  It  arises  in  front  of  the  left  carotid,  and  runs 
obliquely  to  the  right  sternoclavicular  joint,  where 
it  divides  into  the  right  common  carotid  and  right 
subclavian. 

The  common  carotid  arteries  are  identical  in  course, 
branches,  and  relations  in  the  neck,  but  differ  in 
their  origin.  Thus,  the  right  is  a  branch  of  bifurca- 
tion of  the  innominate,  while  the  left  is  a  primary 
branch  of  the  transverse  aorta. 

The  external  carotid  artery  runs  from  the  bifurcation 
of  the  common  carotid  to  the  space  between  the 
neck  of  the  condyle  of  the  mandible  and  the  audi- 
tory meatus,  and  there  divides  into  the  superficial 
temporal  and  internal  maxillary. 

The  internal  carotid  artery  is  a  very  tortuous  vessel, 
and  at  its  origin  is  farther  from  the  median  line  than 
the  external  carotid,  deriving  the  name  "internal" 
from  its  distribution.  For  description  it  is  divided 
into  four  parts:  the  first,  or  cervical;  the  second,  or 
petrous,  is  in  the  carotid  canal;  the  third,  or  cavernous 


DESCRIPTION  OF  THE  ARTERIES 


195 


runs  in  the  cavernous  sinus;  and  the  fourth,  or  cerebral, 
is  the  terminal  portion,  and  supplies  a  portion  of  the 
brain  and  eye-ball. 


Fig.  76 


Applied  anatomy  of  the  arteries  of  the  neck,  showing  the  carotid  and  sub- 
clavian arteries.  The  hypoglossal  nerve  is  not  rightly  placed  in  this  drawing. 
It  forms  the  upper  side  of  a  triangle,  the  two  lower  sides  of  which  are  the 
two  bellies  of  the  digastric.  The  lingual  artery  would  then  run  under  the 
hyoglossus  muscle,  below  the  hypoglossal  nerve.     (Gray.) 


196 


THE  CIRCULATORY  APPARATUS 


The  subclavian  arteries  are  divided  into  three  parts, 
the  first  running  to  the  inner  margin  of  the  scalenus 
anticus;  the  second,  behind  that  muscle;  the  third, 
from  its  outer  border  to  the  lower  border  of  the  first 


Fig.  77 
Nasal.        Palpebral. 


a-orbital. 


Anterior  ethmoidal. 


Posterior  ethmoidal 


Temporal  branche 
of  lachrymal. 


Muscvdar 


Ophthalmic* 


Internal  carotid. 


The  ophthalmic  artery  and  its  branches,  the  roof  of  the  orbit  having  been 
removed.     (Gray.) 


rib,  where  it  becomes  the  axillary  artery.  The  right 
and  left  vessels  differ  only  in  their  first  portions,  the 
right  arising  behind  the  sternoclavicular  joint,  from 
the  innominate;  the  left,  from  the  transverse  aorta  as 
a  primary  branch. 


DESCRIPTION  OF  THE  ARTERIES 


197 


The  basilar  artery,  formed  by  the  two  vertebrals, 
runs  to  the  upper  border  of  the  pons,  and  divides  into 
the  two  posterior  cerebrals.  It  gives  off  the  following 
branches : 

(a)  Several  transverse  arteries  on  each  side.  One 
the  auditory,  enters  the  internal  meatus;  another,  the 
anteroinferior  cerebellar,  to  the  anterior  border  of  the 
cerebellum. 

Fig.  78 


The  axillary  artery  and  its  branches.     (Gray.) 


(6)  The  superior  cerebellar,  to  the  upper  surface, 
joining  the  inferior  cerebellar. 

(c)  The  posterior  cerebrals,  to  the  under  surface  of  the 
posterior  lobes  of  the  cerebrum,  receiving  the  posterior 
communicating.  They  give  off  the  posterior  choroid 
branches  and  supply  the  posterior  perforated  space. 


198  THE  CIRCULATORY  APPARATUS 

The  circle  of  Willis  is  situated  at  the  base  of  the 
brain,  it  is  an  anastomosis  formed  by  the  bloodvessels 
of  the  brain.  The  arteries  entering  into  its  formation 
are:  In  front,  the  two  anterior  cerebral  arteries, 
branches  of  the  internal  carotid,  which  are  connected 
by  the  anterior  communicating  artery ;  behind,  by  two 
posterior  cerebral  arteries,  branches  of  the  basilar,  and 
these  communicate  latterly  with  the  internal  carotids 
through  the  posterior  communicating  arteries. 

The  Arteries  of  the  Upper  Extermity. — The  Axillary 
Artery.  The  axillary  artery  is  the  continuation  of 
the  subclavian.  It  extends  from  the  lower  border  of 
the  first  rib,  where  it  is  deeply  placed,  to  the  lower 
border  of  the  teres  major  tendon,  where  it  is  super- 
ficial, and  there  becomes  the  brachial.  It  is  described 
in  three  parts — the  first,  above  the  pectoralis  minor; 
the  second,  behind  it;  and  the  third,  below  it. 

Branches. — First  part,  superior  and  acromial  thoracic; 
second  part,  long  and  alar  thoracic;  third  part,  sub- 
scapular and  circumflex,  posterior  and  anterior. 

The  Brachial  Artery. — The  brachial  artery  extends 
from  the  end  of  the  axillary,  at  the  lower  border  of 
the  teres  major,  to  J  inch  below  the  elbow-joint,  divid- 
ing into  the  radial  and  ulnar  arteries. 

The  branches  of  the  brachial  artery  are :  The  superior 
profunda,  nutrient  artery,  to  the  humerus,  the  inferior 
profunda,  anastomotica  magna,  and  muscular.. 

The  Radial  Artery. — The  radial  artery  runs  from 
the  bifurcation  of  the  brachial  along  the  radial  side 
of  the  forearm  to  the  WTist,  and  winds  back  to  its  pos- 
terior surface.  It  then  enters  the  palm  through  the 
first  dorsal  interosseous,  and  runs  across  the  hand  to 
form  the  deep  palmar  arch  by  joining  the  deep  branch 
of  the  ulnar,  and  gives  off  in  the  ball  of  the  thumb  the 
superficialis  volse,  a  branch  which  joins  with  the  main 
termination  of  the  ulnar  artery  to  form  the  superficial 
palmar  arch. 


DESCRIPTION  OF  THE  ARTERIES 


199 


The  Ulnar  Artery  runs  along  the  inner  side  of 
the  forearm  to  the  wrist,  crosses  the  annular  ligament 


Fig.  79 


Anastomotica 
magna. 


The  brachial  artery.     (Gray.) 


and  the  palm  of  the  hand,  and  joins  the  superfieialis 
volie  to  form  the  superficial  arch. 


200  THE  CIRCULATORY  APPARATUS 

Fig.  80 


Hadial  recurrent. 


Siiperjiaialis  volae 


The  radial  and  ulnar  arteries     (Gray.) 


DESCRIPTION  OF  THE  ARTERIES  201 

The  superficial  palmar  arch  lies  beneath  the  palmar 
fascia  and  above  the  flexor  tendons  of  the  fingers. 

Fig.  81 


The  abdominal  aorta  and  its  branches  (Gray.) 

The  deep  palmar  arch  lies  beneath  the  flexor  tendons 
and  rests  on  the  metacarpal  bones  and  palmar  inter- 
osseous muscles. 


202 


THE  CIRCULATORY  APPARATUS 


The  Thoracic  Aorta. — The  thoracic  aorta  descends 
from  the  lower  border  of  the  fifth  to  the  front  of  the 
last  dorsal  vertebra. 


Fig.  82 


Ctjstic  artery. 


The  celiac  axis  and  its  branches,  the  liver  having  been  raised  and  the 
lesser  omentum  removed. 


The  Abdominal  Aorta. — The  abdominal  aorta  runs 
from  the  last  dorsal  to  the  left  side  of  the  middle  of 
the  fourth  lumbar  vertebra,  there  dividing  into  the 
two  common  iliacs. 

The  branches  of  the  thoracic  aorta: 

Nine  pairs  of  intercostal  arteries,  two  subcostal, 
bronchial,  esophageal,  mediastinal,  and  pericardial. 


DESCRIPTION  OF  THE  ARTERIES  203 

The  branches  of  the  abdominal  aorta : 

(a)  Parietal  and  (b)  visceral. 

The  Parietal  Branches. — (1)  The  phrenic,  (2)  the 
lumbar,  (3)  the  middle  sacral. 

The  Visceral  Branches. — I.  The  celiac  axis,  J 
inch  long,  divides  into  the  gastric,  hepatic,  and  splenic. 
It  is  covered  by  the  lesser  omentum,  rests  below  on 
the  pancreas;  on  each  side  is  a  semilunar  ganglion  and 
on  the  right  the  lobus  Spigelii,  of  the  liver  on  the  left 
the  stomach. 

Branches. — (a)  The  gastric  artery  runs  to  the  cardiac 
orifice  of  the  stomach,  thence  to  the  right,  along  the 
lesser  curvature,  in  the  lesser  omentum  as  far  as  the 
pylorus.  It  supplies  both  surfaces  of  the  stomach  and 
the  esophagus,  anastomosing  with  the  splenic,  hepatic, 
and  esophageal  arteries. 

(6)  The  hepatic  artery  passes  below  the  foramen  of 
Winslow  to  the  pylorus,  then  ascends  in  the  lesser 
omentum,  anterior  to  that  foramen,  and  to  the  left 
of  the  gall  duct,  to  the  transverse  fissure  of  the  liver, 
and  divides  into  a  right  and  a  left  branch.  Its  pyloric 
branch  passes  along  the  lesser  curvature  to  meet  the 
gastric.  Its  cystic  branch  from  the  right  division 
ascends  on  the  neck  of  the  gall-bladder  and  supplies 
it  by  two  branches.  The  other  branch  of  the  hepatic, 
the  gastroduodenalis,  divides  behind  the  lower  part 
of  the  duodenum  into  a  superior  pancreaticoduodenal 
branch,  descending  between  the  pancreas  and  duo- 
denum to  join  the  inferior  artery  of  the  same  name; 
and  the  right  gastro-epiploica,  passing  into  the  omentum 
toward  the  left,  along  the  great  curvature,  to  meet 
the  left.     (See  Fig.  82.) 

(c)  The  splenic  runs  tortuously  to  the  left,  along 
the  upper  border  of  the  pancreas,  and  divides  near 
the  spleen  into  branches  which  enter  at  the  hilum, 
some  passing  to  the  stomach. 

Branches. — Pancreatic,  numerous,  small;  and  one 
larger,  the  pancreatica  magna,  accompanies  the  duct 
of  Wirsung. 


204 


THE  CIRCULATORY  APPARATUS 


Five  to  seven  vasa  brevia,  in  the  gastrosplenic  omen- 
tum, to  great  end  of  the  stomach,  joining  the  gastric 
and  gastro-epiploic  vessels.     (See  Fig.  82,  page  202.) 


Fig.  83 


Superior  mesenteric  artery.     (Testut.) 


The  left  gastro-epiploica  runs  to  the  right,  along  the 
great  curvature,  to  join  the  right. 


DESCRIPTION  OF  THE  ARTERIES  205 

II.  The  superior  mesenteric  supplies  the  small  intes- 
tine except  the  first  part  of  the  duodenum,  as  well  as 
the  cecum,  appendix,  ileum,  and  ascending  and  trans- 
verse colon.  Emerging  from  between  the  transverse 
duodenum  and  pancreas,  it  crosses  the  former,  and 
descends  in  the  mesentery  to  the  right  iliac  fossa  with 
its  veins  and  a  plexus  of  nerves.  It  ends  by  anasto- 
mosing with  its  own  ileocolic  branch.     (See  Fig.  83.) 

III.  The  inferior  mesenteric  supplies  the  descending 
colon,  sigmoid  flexure,  and  upper  part  of  the  rectum, 
and  its  continuation.     (See  Fig.  83.) 

IV.  The  suprarenals,  to  the  under  surface  of  the 
suprarenal  capsules,  join  branches  of  the  phrenic  and 
renal  arteries. 

V.  The  renal,  to  the  hilum  of  the  kidney,  enters  by 
four  or  five  branches,  into  which  each  vessel  divides 
close  to  the  kidney. 

VI.  The  spermatic,  the  ovarian  in  the  female,  to 
the  testicles  or  ovaries  respectively. 

The  Iliac  Arteries. — The  common  iliac  arteries  run 
downward  and  outward  from  the  division  of  the 
aorta  to  the  lumbosacral  joint,  and  divide  into  the 
external  and  internal  iliacs.     (See  Fig.  81,  page  201.) 

The  internal  iliac  artery  descends  to  the  upper  part 
of  the  great  sacrosciatic  foramen,  and  divides  into  an 
anterior  and  a  posterior  trunk. 

The  posterior  trunk  gives  off  the  following  branches: 
(a)  the  iliolumbar;  (6)  the  lateral  sacral;  (c)  the  gluteal, 
passes  through  the  great  sciatic  foramen,  and  divide 
into  a  superficial  and' a  deep  branch. 

The  anterior  trunk  of  the  internal  iliac  gives  off  the 
following  branches: 

(a)  The  superior  vesical  represents  the  pervious  part 
of  the  fetal  hypogastric  artery.  It  runs  to  the  apex 
and  body  of  the  bladder  and  to  the  ureter,  joins  its 
fellow,  and  gives  off  the  artery  of  the  vas  deferens, 
which  accompanies  that  structure  to  the  testicle.     It 


206  THE  CIRCULATORY  APPARATUS 

also  generally  gives  off  the  (b)  middle  vesical  to  the 
base  of  the  bladder. 

(c)  The  inferior  vesical — vaginal  in  the  female — 
joins  its  fellow.  It  supplies  the  bladder,  prostate 
gland,  and  seminal  vesicles;  in  the  female,  vagina,  and 
rectum. 

(d)  The  middle  hemorrhoidal  arises  with  the  pre- 
ceding, and  runs  to  the  rectum  to  join  other  hemor- 
rhoidal arteries. 

(e)  The  uterine  in  the  female  ascends  in  the  broad 
ligament  from  the  cervix  along  the  side  of  the  uterus, 
and  joins  the  ovarian  artery. 

(/)  The  obturator  runs  forward  below  the  pelvic 
brim,  between  the  peritoneum  and  pelvic  fascia  below 
the  nerve,  then  through  the  upper  part  of  the  obtura- 
tor foramen,  dividing  beneath  the  obturator  externus 
into  an  external  and  an  internal  branch. 

The  termination  of  the  anterior  trunk  of  the  internal 
iliac  then  divides  into  two  branches,  the  sciatic  and 
the  internal  pudic  arteries. 

The  external  iliac  artery  extends  from  the  division 
of  the  common  iliac  to  the  midpoint  between  the 
symphysis  of  the  pubis  and  the  anterior  superior 
spine  of  the  ilium,  behind  Poupart's  ligament. 

The  Arteries  of  the  Lower  Extremity. — The  Femoral 
Artery. — ^The  femoral  artery  continues  the  external 
iliac  artery  down  into  the  thigh  to  end  at  the  opening 
in  the  adductor  magnus  at  the  junction  of  the  upper 
three-fourths  and  lower  one-fourth  of  the  femur. 
From  its  beginning  to  the  point  where  the  profunda 
femoris  is  given  off,  it  is  called  the  common  femoral, 
below  this  the  superficial  femoral.  Its  upper  part 
lies  in  Scarpa's  triangle,  bounded  above  by  Poupart's 
ligament,  the  inner  side  formed  by  the  inner  margin 
of  the  adductor  longus,  the  outer  by  the  sartorius. 
Its  floor,  from  without  inward,  is  made  up  of  the 
iliacus,  psoas,  pectineus,  and  adductor  brevis.  The 
lower  part  runs  in  Hunter's  canal,  a  depression  between 


DESCRIPTION  OF  THE  ARTERIES 


207 


the  vastus  internus  and  the  adductores  magnus  and 
longus,  covered  by  a  strong  fascia  passing  between 
them. 

Fig.  84 


Long  saphenous 
nerve. 


Superior  external 
articular. 


Inferior  external 
articular. 


Anterior  tibial    (\  \  \j 
recurrent. 


Ana^iomolica 
magna. 
—Superior  inicrnal 
articular. 


Inferior  internal 
ariiada/r. 


The  femoral  artery.     (Gray.) 


208  THE  CIRCULATORY  APPARATUS 

The  Popliteal  Artery. — ^The  popliteal  artery  runs 
from  the  adductor  opening  to  the  lower  border  of  the 
popliteus,  passing  through  the  popliteal  space  at  the 
back  of  the  knee-joint,  where  it  divides  into  the  ante- 
rior and  posterior  tibial. 

The  anterior  tibial  artery  runs  from  the  lower  border 
of  the  popliteus,  between  the  heads  of  the  tibialis 
posticus  and  above  the  interosseous  membrane,  to 
the  front  of  the  leg,  then  descends  as  far  as  the  ankle, 
ending  in  the  dorsalis  pedis. 

The  dorsalis  pedis  is  the  continuation  of  the  anterior 
tibial,  and  runs  from  the  bend  of  the  ankle  to  the  first 
interosseous  space,  where  it  divides  into  the  dorsalis 
hallucis  and  plantar  digital. 

The  plantar  digital  branch  of  the  dorsalis  pedis 
artery  passes  between  the  heads  of  the  first  dorsal 
interosseous,  joins  with  the  external  plantar  to  form 
the  plantar  arch,  and  after  supplying  the  inner  side 
of  the  great  toe,  divides  into  two  branches  for  the 
adjacent  sides  of  the  great  and  second  toes. 

The  posterior  tibial  artery  runs  from  the  lower  border 
of  the  popliteus  to  divide,  between  the  inner  malleolus 
and  heel,  into  the  external  and  internal  plantar  arteries. 

The  plantar  arteries  are  the  terminal  branches  of 
the  posterior  tibial.  The  internal  is  at  first  under 
cover  of  the  abductor  pollicis,  and  then  between  it 
and  the  flexor  brevis  digitorum,  anastomosing  at  the 
inner  border  of  the  great  toe  with  its  digital  artery. 

The  external,  the  larger,  passes  to  the  base  of  the 
fifth  metatarsal,  then  to  the  space  between  the  first 
and  second  metatarsals,  and  joins  the  plantar  digital, 
from  the  dorsalis  pedis,  to  form  the  plantar  arch. 

The  plantar  arch  supplies  the  muscles,  fascia,  and 
skin  of  the  sole  of  the  foot,  and  gives  off  the  posterior 
perforating.  These  pierce  the  three  outer  spaces 
between  the  heads  of  the  dorsal  interossei  and  join 
the  dorsal  interosseous  arteries. 

The  digital,  four  in  number,  supply  the  three  outer 


DESCRIPTION  OF  THE  ARTERIES 

Fia.  85 


209 


CommumiciUing. 


Applied  anatomy  of  the  anterior  tibial  and  dorsalis  pedis  arteries.    (Gray.) 
1-4 


210 


THE  CIRCULATORY  APPARATUS 


toes  and  the  outer  half  of  the  second  toe;  the  first 
runs  to  the  outer  side  of  the  little  toe,  the  others 
bifurcate  to  the  adjacent  sides  of  the  fourth  and 
fifth,  fourth  and  third,  third  and  second  toes.  At 
the  point  of  bifurcation  each  sends  a  small  branch 
to  join  the  dorsal  interosseous  arteries  {anterior 
perforating). 

Fig.  86 


ZIommuuicating 

branch  of 
dorsalis  pedis. 
Its  digital 
branches. 


The  plantar  arteries.    Deep  view.     (Gray.) 


DESCRIPTION  OF  THE  VEINS 

The  Systemic  Veins. — These  are  divided  into  three 
sets:  superficial,  deep,  and  sinuses. 


DESCRIPTION  OF  THE  VEINS  211 

The  superficial  veins  are  usually  found  between  the 
layers  of  the  fasciae  just  beneath  the  skin. 

The  deep  veins  accompany  the  arteries,  as  a  rule, 
and  are  usually  found  in  the  same  sheath,  derived 
from  the  deep  fascia.  They  are  generally  in  pairs, 
one  on  each  side  of  the  artery,  and  are  termed  venae 
comites.  The  larger  arteries  have  only  one  accom- 
panying vein — as  the  axillary,  subclavian,  popliteal, 
femoral. 

Sinuses  are  venous  channels  found  in  the  skull, 
which  drain  the  blood  from  the  brain  and  its  mem- 
branes, and  ultimately  communicate  with  the  right 
and  left  internal  jugular  veins  at  the  base  of  the 
skull.  Some  are  found  between  two  layers  of  the  dura, 
and  others  lodged  in  grooves  on  the  inner  surfaces  of 
the  cranial  bones,  ensheathed  by  the  dura.  They  are 
lined  by  endothelial  cells  continuous  with  that  which 
lines  the  veins.  They  are  sixteen  in  number — six 
single  and  ten  paired. 

Venous  plexus  is  the  name  given  to  a  number  of 
small  veins  communicating  with  each  other  and 
arranged  in  a  net-work  surrounding  or  within  any 
organ  or  part  of  the  body. 

The  Veins  of  the  Heart. — ^The  great  cardiac  vein 
ascends  in  the  anterior  interventricular  groove  from 
the  apex  of  the  heart  to  the  left  auriculoventricular 
groove ;  along  this  latter  it  runs  to  the  posterior  surface 
of  the  heart,  to  end  in  the  coronary  sinus.  At  its 
termination  it  is  provided  with  a  valve. 

The  right  (small)  coronary  vein  in  the  right  auriculo- 
ventricular groove  to  the  sinus. 

The  coronary  sinus,  one  inch  long,  is  placed  at  the 
back  part  of  the  auriculoventricular  groove,  on  the 
left  side,  and  opens  into  the  right  auricle  in  front  of 
the  inferior  vena  cava. 

The  Superior  Vena  Cava  and  Innominate  Veins. — ^The 
superior  vena  cava  is  a  large  trunk  formed  by  the 
union  of  the  two  venae  innominatae,  and  returns  the 


212  THE  CIRCULATORY  APPARATUS 

blood  from  the  head  and  neck,  the  thoracic  walls,  and 
the  upper  extremities.  It  is  about  three  inches  long, 
and  descends  from  the  junction  of  the  first  right  costal 
cartilage  with  the  sternum  to  its  termination  in  the 
right  auricle,  opposite  the  upper  border  of  the  third 
right  cartilage. 

The  Veins  of  the  Head  and  Neck. — The  facial  vein 
runs  from  the  inner  angle  of  the  eye  to  the  anterior 
border  of  the  masseter  muscle,  then  backward  below 
the  jaw,  joining  the  anterior  division  of  the  temporo- 
maxillary  trunk  to  form  the  common  facial,  which 
joins  the  internal  jugular. 

The  temporomaxillary  vein  (posterior  facial)  is  a  short 
trunk,  formed  by  the  temporal  and  internal  maxillary 
veins. 

The  temporal  vein  is  formed  by  the  union  of  the 
superficial  with  the  middle  temporal  vein,  and  crosses 
over  the  zygoma  and  under  the  parotid  to  join  the 
internal  maxillary  vein. 

The  external  jugular  vein  is  formed  by  the  union  of 
the  posterior  auricular  and  the  posterior  division  of 
the  temporomaxillary  trunk.  It  descends  obliquely 
across  the  sternomastoid,  lying  betw^een  the  platysma 
and  fascia.  Above  the  clavicle  it  pierces  the  fascia 
and  joins  the  subclavian  at  the  outer  border  of  the 
scalenus  anticus;  sometimes  it  joins  the  internal 
jugular. 

The  internal  jugular  vein  commences  at  the  jugular 
foramen  just  below  the  junction  of  the  inferior  petrosal 
with  the  lateral  sinus,  and  descends  with  the  external 
carotid,  then  with  the  common  carotid,  to  join  at  a 
right  angle  with  the  subclavian  vein  behind  the 
clavicle,  thus  forming  the  innominate  vein.  It  is 
placed  external  to  the  carotid  vessels,  lying  in  the 
same  sheath  with  each  in  turn. 

The  Veins  of  the  Upper  Extremity. — The  Superficial 
Veins. — They  commence  from  a  plexus  on  the  back 


DESCRIPTION  OF  THE  VEINS  213 

of  the  hand  mostly,  but  to  some  extent  from  the  palm. 
They  comprise  the  following: 

The  ulnar,  anterior  and  posterior,  uniting  above  in 
the  common  ulnar. 

The  radial  vein  is  situated  on  the  outer  side,  and 
the  median  ascends  mesially,  receives  a  deep  median 
vein,  and  divides  at  the  bend  of  the  elbow  into  the 
median  basilic  and  median  cephalic. 

The  median  basilic  joins  the  common  ulnar  to  form 
the  basilic.  The  bicipital  fascia  separates  it  from  the 
brachial  artery. 

The  median  cephalic  crosses  the  external  cutaneous 
nerve,  and  joins  the  radial  to  form  the  cephalic. 

The  basilic  runs  along  the  inner  side  of  the  biceps, 
pierces  the  fascia,  and  is  continued  upward  into  the 
axillary  vein. 

The  cephalic  runs  along  the  outer  side  of  the  biceps, 
and  between  the  pectoralis  major  and  deltoid,  piercing 
the  costocoracoid  membrane  to  join  the  axillary  vein 
below  the  clavicle. 

The  Deep  Veins. — The  axillary  vein  begins  where 
the  venae  comites  of  the  brachial  artery  and  the  basilic 
vein  unite.  It  runs  internal  to  the  artery,  and  receives 
veins  corresponding  to  its  branches,  as  well  as  the 
cephalic. 

The  subclavian  vein  is  the  continuation  upward  of 
the  axillary,  and  runs  at  a  lower  level  than  its  artery, 
from  which  it  is  separated  by  the  phrenic  nerve  and 
scalenus  anticus,  to  the  inner  border  of  that  muscle, 
to  join  the  internal  jugular,  forming  the  innominate. 
It  receives  the  external  jugular,  and  occasionally  the 
aiiterior. 

The  Inferior  Vena  Cava. — This  large  trunk  arises 
at  the  fifth  lumbar  by  the  union  of  the  two  common 
iliacs.  It  ascends  to  the  right  of  the  aorta,  grooves 
the  posterior  border  of  the  liver,  pierces  the  diaphragm, 
is  enclosed  by  the  serous  layer  of  the  pericardium, 
and  empties  into  the  right  auricle. 


214  THE  CIRCULATORY  APPARATUS 

Fig.  87  Fig.  88 


Median  cephalic. 


External 
cidaneuus  nerve. 


The  superficial  veins  of  the  flexor 
aspect  of  the  upper  extremity. 


The  internal  or  long  saphenous  vein 
and  its  tributaries.     (Gray  ) 


DESCRIPTION  OF  THE  VEINS  215 

The  Veins  of  the  Lower  Extremity. — The  Superficial 
Veins. — They  begin  on  the  back  of  the  foot  in  a 
plexus  which  receives  the  digital  veins,  and  forms  an 
arch  from  which -emerge  the  internal  or  long  and  the 
external  or  short  saphenous  veins. 

The  long  (internal)  saphenous,  from  the  inner  part  of 
the  plexus,  runs  in  front  of  the  inner  malleolus  of  the 
tibia,  along  with  the  long  saphenous  nerve,  behind  the 
inner  border  of  the  tibia  and  condyle  of  the  femur; 
thence  up  along  the  antero-internal  part  of  the  thigh 
to  join  the  femoral  vein  at  the  saphenous  opening. 

The  short  (external)  saphenous  vein  ascends  behind 
the  outer  malleolus,  and  external  to  the  tendo  Achillis, 
with  the  external  saphenous  nerve,  and  pierces  the  deep 
fascia  in  the  popliteal  space  to  join  the  popliteal  vein. 

The  Deep  Veins. — These  are  the  venos  comites 
of  the  arteries.  The  posterior  tibial  veins  receive  the 
peroneal,  and  join  the  anterior  tibial  to  form  the  pop- 
liteal. This  vessel  then  ascends,  crossing  superficial 
to  the  artery,  from  the  inner  to  the  outer  side,  and 
becomes  the  femoral  at  the  opening  in  the  lower 
border  of  the  adductor  magnus  muscle.  It  receives 
the  external  saphenous  and  veins  corresponding  to  the 
arterial  branches. 

The  femoral  vein  accompanies  the  artery,  and 
becomes  the  external  iliac  at  Poupart's  ligament.  It 
is  at  first  outside,  then  behind,  and  at  its  termination 
internal  to,  the  artery  as  it  lies  in  Hunter's  canal.  It 
receives,  in  its  lower  part,  veins  corresponding  to  the 
branches  of  the  superficial  femoral  artery;  the  long 
saphenous,  and  the  inofunda  vein. 

The  external  iliac  joins  the  internal  iliac  near 
the  lumbosacral  articulation,  being  at  first  internal 
to,  later  behind,  the  artery,  and  they  empty  into  the 
common  iliac  vein  on  either  side,  the  latter  tocming 
the  inferior  vena  cava. 

The  Portal  System. — ^The  portal  vein,  three  inches 
long,  arises  from  the  union  of  the  splenic  and  superior 


216  THE  CIRCULATORY  APPARATUS 

mesenteric  veins  behind  the  head  of  the  pancreas, 
and  ascends  behind  the  duodenum  and  between  the 
layers  of  the  lesser  omentum.  Here  it  runs  behind 
the  hepatic  artery  and  bile  duct.  Accompanied  by  the 
hepatic  plexus  of  nerves  and  lymphatics,  all  enclosed 
in  Glisson's  capsule,  it  then  enters  the  transverse 
fissure,  forming  near  the  right  end  the  "sinus,"  and 
divides  into:  A  right  branch,  to  the  right  lobe,  which 
distributes  branches  entering  the  hepatic  substance 
with  the  hepatic  arterial  branches  and  ducts;  and  a 
left  branch,  distributed  like  the  right.  The  portal  vein 
also  drains  the  pyloric,  cystic,  gastric,  and  par- 
umbilical  veins.  The  portal  vein  and  its  tributaries 
convey  blood  to  the  liver  from  the  following  organs 
— spleen,  pancreas,  stomach,  gall-bladder,  umbilicus, 
duodenum,  small  and  large  intestines,  appendix,  and 
upper  portion  of  the  rectum. 

The  vena  portse  receives  the  following  tributaries: 

The  superior  mesenteric  corresponding  to  the  artery 
of  the  same  name,  receiving  also  the  right  gastro- 
epiploic win,  besides  branches  accompanjdng  those 
of  the  artery.    It  joins  the  splenic  vein. 

The  splenic  arises  by  five  or  six  vessels  uniting  after 
leaving  the  hilum,  and  runs  to  the  right  below  the 
artery,  joining  the  above  at  a  right  angle  to  form  the 
vena  portee.  It  receives  the  vasa  brevia,  left  gastro- 
epiploic, and  pancreatic  branches,  and  the  inferior 
mesenteric  vein.     • 

The  inferior  mesenteric  vein  corresponds  in  branches 
and  course  to  the  artery,  and  empties  into  the  angle 
of  junction  of  the  two  preceding. 

The  pyloric  runs  with  the  pyloric  branch  of  the 
hepatic  artery,  and  joins  the  vena  portse;  also  the 
gastric  vein  which  accompanies  the  gastric  artery  and 
receives  the  esophageal  branches,  joins  the  vena  portse 
above  the  former.^ 

^  See  Chapter  on  Absorption,  page  287,  for  description  of  the  func- 
tion of  the  portal  system. 


BLOOD  217 


BLOOD 


The  blood  is  contained  in  the  bloodvessels,  which 
are  practically  a  closed  arrangement  of  tubes — the 
arteries,  veins,  and  their  connecting  capillaries. 

Function. — The  function  of  the  blood  is  to  transmit 
the  various  nutritive  elements,  absorbed  from  the 
organs  of  digestion  to  the  tissues  of  the  body,  to  carry 
to  the  tissues  oxygen  absorbed  from  the  air  in  the 
lungs;  to  remove  from  the  tissues  the  various  waste 
products,  such  as  urea,  uric  acid,  w^ater  through  the 
kidneys  and  skin,  carbon  dioxide  (CO2) — the  lattei^ 
being  carried  to  the  lungs  by  the  red  cells  which  give 
it  off  with  the  expired  air;  to  maintain  the  temperature 
of  the  body  in  warm-blooded  animals. 

,  Physical  Characteristics. — Blood  is  alkaline  in  reac- 
tion, opaque  in  color,  and  appears  as  a  homogeneous 
mass.  Two  kinds  of  blood  are  contained  in  the  vascular 
system — in  the  arteries  it  is  bright  red  in  color,  while 
in  the  veins  it  is  dark  bluish  in  color.  The  color  of 
the  blood  is  due  to  the  coloring  matter — hemoglobin — 
contained  in  the  red  cells.  The  bright  red  color  of 
normal  blood  is  due  to  the  hemoglobin  in  combination 
with  the  oxygen,  which  it  absorbs  on  coming  in  contact 
with  the  air  in  the  lungs.  The  bluish  color  of  venous 
blood  is  due  to  the  hemoglobin  absorbing  the  carbon 
dioxide  from  the  tissues — a  waste  compound  which  is 
being  carried  to  the  lungs  to  be  given  off  in  the  expired 
air. 

Constituents  of  Blood. — It  consists  of  a  liquid  por- 
tion called  the  liquor  sanguinis  or  plasma,  red  cells 
or  erythrocytes,  white  cells  or  leukocytes,  and  blood 
plaques.  (Of  course  the  latter  can  only  be  seen  with 
the  microscope.) 

The  Plasma. — This  is  a  clear,  slightly  yellowish, 
transparent  fluid,  consisting  mostly  of  the  nutritive 
elements  of  the  foods — proteins,  carbohydrates,  fats, 
inorganic  salts — ^which  have  been  rendered  possible 


218  THE  CIRCULATORY  APPARATUS 

of  absorption  by  the  process  of  digestion;  and  waste 
products  (urea,  cholesterin,  etc.,  resulting  from  the 
breaking  down  of  tissues  following  their  functional 
activities),  which  are  carried  to  the  kidneys,  lungs, 
and  skin  to  be  eliminated. 

Serum. — Serum  is  a  clear,  transparent,  straw-colored 
fluid  formed  when  blood  coagulates  or  clots,  due  to 
the  contraction  of  the  fibrin  which  separates  after 
several  hours,  following  withdrawal  or  is  found  by 
whipping  the  blood  with  twigs,  upon  which  the  fibrin 
forms  as  whitish  threads.  The  serum  consists  prac- 
tically of  the  same  substances  as  the  plasma,  excepting 
the  proteins  which  are  found  in  the  fibrin. 

Serum-albumin  represents  the  protein  constituents 
of  the  blood  found  in  the  plasma.  It  is  absorbed 
from  the  digestive  tract  in  the  form  of  peptones  which 
are  formed  from  the  proteins  in  a  manner  not  definitely 
decided  upon  by  physiologists.  It  replaces  the  proteins 
which  have  been  used  up  in  the  disintegration  of  tissues 
(anabolism) . 

Paraglobulin  is  supposed  to  be  similar  to  serum- 
albumin  as  regards  its  function,  and  can  only  be 
isolated  from  the  blood  serum  by  chemical  methods. 

Fibrinogen  is  found  in  the  blood,  plasma,  lymph,  peri- 
cardial, and  peritoneal  fiuids.  It  can  only  be  studied 
by  treating  blood  by  chemical  means  before  coagulation. 
Its  importance  in  regard  to  its  function  and  nutritive 
values  is  an  undetermined  quantity,  aside  from  the 
fact  that  it  contributes  to  the  formation  of  fibrin. 

Fat  is  found  in  the  serum  as  microscopic  globules. 
The  amount  is  very  small  (0.25  per  cent.);  however, 
after  a  hearty  meal  the  quantity  is  increased. 

Sugar  is  present  in  the  form  of  dextrose,  which  is 
a  member  of  the  carbohydrate  group  of  body  con- 
stituents derived  from  fruits,  cereals,  etc.,  taken  as 
foods. 

Extractives  include  the  nitrogenized  bodies,  urea, 
uric  acid,  creatin,  xanthin,  etc.,  various  chemical  com- 


BLOOD  219 

binations  and  decompositions,  which  result  from  the 
breaking  down  of  muscle  and  nerve  tissues.  They 
occur  in  very  small  amounts,  being  continually  absorbed 
from  the  tissues  by  the  blood,  but  seldom  accumulate, 
as  they  are  rapidly  and  continually  passed  off  through 
the  kidneys,  bowels,  skin,  etc. 

Inorganic  Salts. — Sodium  and  potassium  chlorides, 
phosphates  and  sulphates,  calcium  and  magnesium 
phosphates  are  found  in  the  plasma.  Sodium  chloride 
is  the  most  important.  The  alkalinity  of  the  blood  is 
due  to  the  contained  salts,  some  of  which  are  alkaline 
in  reaction. 

The  Red  Cells. — Red  cells,  corpuscles,  or  erythrocytes 
are  seen  after  a  drop  of  freshly  drawn  blood  is  examined 
under  the  microscope.  They  appear  as  disk-like 
cells,  floating  or  swimming  about  in  the  blood  plasma. 
After  a  few  minutes  they  will  be  seen  to  group  them- 
selves in  a  number  of  columns  of  varying  lengths, 
resembling  rolls  of  coins.  Also  a  few  white  cells  will 
be  seen  floating  about  in  the  plasma. 

A  single  cell  is  slightly  yellow  or  greenish.  Numbers 
when  collected  together  appear  red.  The  color  is  due 
to  the  presence  within  the  cell  of  the  coloring  matter, 
hemoglobin.  The  diameter  of  a  red  cell  is  ^yV o^  of  an 
inch  or  0.0075  mm.;  i2\~q'^  or  0.0019  mm.  in  thickness. 
The  average  number  of  red  cells  in  one  cubic  milli- 
meter of  blood  is  5,000,000  for  the  male;  4,500,000 
for  the  female. 

Chemic  Composition. — The  corpuscle  consists  of 
hemoglobin,  about  30  per  cent,  of  total  weight,  the 
rest,  70  per  cent.,  contains  68  per  cent,  water,  2  per 
cent,  solid  matter,  e.  g.,  cholestrin,  lecithin,  and 
inorganic  salts. 

The  function  of  the  red  cell  is  to  carry  oxygen  to 
the  tissues,  where  it  enters  into  combination  with 
them  (oxidation).  This  phenomenon  is  made  possible 
by  the  hemoglobin  contained  in  the  red  corpuscle. 
When  the  red  cells  in  the  blood   come  in  contact. 


220  THE  CIRCULATORY  APPARATUS 

under  the  oxygen  pressure,  with  the  air  we  breathe 
into  our  lungs,  the  hemoglobin  absorbs  some  of  the 
oxygen,  through  a  chemical  union  (oxyhemoglobin); 
immediately  the  blood  becomes  bright  scarlet  color 
on  leaving  the  lungs;  as  the  tissues  are  reached  by 
this  blood,  when  the  oxygen  pressure  is  low,  the 
oxyhemoglobin  gives  up  some  of  its  oxygen  to  the 
tissues,  and  the  blood  becomes  bluish  in  color  (reduced 
blood);  whereupon  it  returns  through  the  veins  to 
the  lungs  by  way  of  the  heart,  to  be  oxidized  again. 

The  White  Cells. — The  white  cells,  corpuscles,  or 
leukocytes  are  composed  chemically  of  90  per  cent, 
water,  the  balance  solid  matter,  mostly  proteins,  e.  g., 
nuclein,  nucleo-albumin,  which  contain  phosphorus  (as 
much  as  10  per  cent.),  cell  globulin,  also  lecithin,  fat, 
glycogen,  earthy  and  alkaline  phosphates. 

The  number  of  white  corpuscles  is  much  less  than 
the  red  corpuscles,  thus  in  1  cubic  millimeter  the 
ratio  is  about  1  white  to  700  red.  The  average  number 
of  white  cells  in  a  cubic  millimeter  of  blood  is  between 
7500  to  8000.  The  number  may  be  increased  or  reduced 
by  the  following  physiologic  conditions:  Taking  of 
food  rich  in  proteins  raises  the  number  30  to  40  per 
cent.;  in  the  newborn,  17,000  to  20,000  per  cubic 
millimeter;  latter  days  of  pregnancy  they  are  as  high 
as  15,000  to  20,000;  they  are  increased  in  various 
pathologic  conditions,  such  as  abscess,  peritonitis, 
appendicitis,  pneumonia.  Starvation  reduces  the 
number. 

The  white  cells  as  seen  under  the  microscope  floating 
in  the  blood  plasma,  appear  as  grayish  cells,  about 
2-:5Vo'  inch  in  diameter,  adhering  to  the  walls  of  the 
vessel. 

The  cell  structure  appears  as  a  homogeneous  mass 
containing  numerous  granules  consisting  of  fat,  pro- 
tein, and  carbohydrate.  A  nuclei  can  be  seen  by 
the  adding  of  a  mild  acid.  They  are  ameboid,  that  is, 
they  show  movements  similar  to  those  seen  in  the 


BLOOD  221 

amebae.  As  a  result  of  this  ameboid  movement  they 
assume  a  different  shape  from  time  to  time.  White 
cells  have  the  properties  of  moving  about  and  coming 
in  contact  with  bacteria,  and  disintegrated  tissues,  then 
can  be  seen  taking  them  into  their  substance  and  elimi- 
nating them  from  the  cell  or  digesting  the  invader. 
They  can  by  their  movements  slip  through  the  wall 
of  the  capillary  vessel  and  appear  in  the  adjacent 
lymph  spaces.  This  power  of  the  white  cell  is  best 
appreciated  in  the  early  stages  of  inflammation  when 
the  blood  stream  is  always  engorged  with  red  and  white 
corpuscles;  the  latter  can  be  seen  passing  into,  through, 
and  outside  the  wall,  and  preparing  to  combat  the 
invading  germ  causing  the  trouble.  This  action  of 
the  white  corpuscles  is  called  diapedesis. 

The  large  and  small  lymphocytes  originate  in  the 
lymph  glands,  the  solitary  and  combined  glands  of 
the  intestines,  etc.  They  are  carried  into  the  blood 
stream  from  these  glands  by  means  of  the  flowing 
lymph.  The  polymorphonuclear,  eosinophiles,  baso- 
philes,  and  leukocytes  are  derived  from  the  bone- 
marrow  only.  They  reach  the  circulation  by  entering 
the  capillaries  in  the  bone-marrow.  Leukocytes  dis- 
appear by  a  process  of  dissolution.  The  period  of 
their  life  is  unknown. 

Function  of  White  Cells. — The  polymorphonuclear, 
large  and  small,  h  mphocytes  possess  the  properties 
of  engaging  and  removing  bacteria  and  broken-down 
tissue.  They  attack  and  destroy  more  or  less  effec- 
tively forms  of  intruding  bacteria  by  surrounding, 
and  incorporating  the  tissue  or  bacterium  and  elimi- 
nating them  by  a  process  of  digestion.  This  swallowing 
action  of  these  white  cells  caused  Professor  Metchni- 
koff  to  call  them  phagocytes,  and  the  process  as  phago- 
cytosis. Thus  these  scavengers  aid  the  human  body 
in  recovering  from  disease  by  combating  and  destroy- 
ing the  invading  bacterium.  White  cells  are  supposed, 
after    breaking    up,    to    contribute    certain    protein 


222  THE  CIRCULATORY  APPARATUS 

material   to   the   blood   plasma,   which   aids   in   the 
coagulation  of  blood. 

Blood  Plaques. — ^These  are  colorless  disks  con- 
sisting of  protoplasm.  Their  diameter  is  1.5  to  3.5 
micromillimeters.  The  number  compared  to  the  red 
cells  is  1  to  18  or  20.  They  are  concerned  mostly 
with  the  coagulation  of  the  blood,  by  their  adhering 
and  forming  irregular  masses  (Schultze),  acting  as  a 
nucleus  for  the  fibrin  filaments  to  spread  from  during 
coagulation  of  the  blood.  They  can  only  be  seen 
microscopically  after  subjecting  the  blood  to  treat- 
ment with  osmic  acid. 

Coagulation  of  Blood. — Blood  when  freshly  drawn  from 
a  living  body  into  a  vessel  is  fluid.  In  a  short  time 
it  becomes  thickened  or  viscid,  this  increase  in  con- 
sistency becomes  more  marked  ,until  the  vessel  con- 
tains a  dark  reddish  mass,  resembling  gelatin.  Shortly 
a  few  drops  of  fluid  appear  on  the  surface  of  the  mass, 
which  gradually  increases  in  amount,  the  vessel  is 
seen  to  contain  a  deposit  of  a  firm,  organized  mass 
— the  clot — floating  in  a  reddish-yellow  fluid — the 
blood-serum.  On  examining  a  portion  of  the  clot 
microscopically,  it  will  show  threads  of  fibrin  with 
red  and  white  corpuscles  clinging  to  them. 

The  Clotting  of  Blood. — This  is  supposed  to  be  a 
chemic  phenomenon  due  to  the  action  of  a  ferment, 
derived  from  calcium  chloride,  and  some  authors 
suggest  leukocytes  acting  on  the  fibrinogen  of  the 
blood  plasma,  and  converting  it  into  fibrin  and  thus 
forming  the  nucleus  of  the  clot.  If  blood  is  freshly 
drawn  into  a  vessel,  then  whipped  with  a  bundle  of 
fine  twigs  for  a  few  moments,  the  fibrin  will  be  deposited 
on  these  twigs  as  whitish  threads.  Blood  treated  in 
this  manner  will  not  clot  when  left  in  the  vessel;  the 
serum  will  be  the  only  residue  present.  This  blood, 
treated  as  above,  is  called  defibrinated. 


QUESTIONS  223 


QUESTIONS 

1.  Where  is  the  pericardium  found?    Its  function? 

2.  In  which  bony  cavity  of  the  body  is  the  heart  located? 

3.  What  is  the  position  of  the  heart  in  the  thoracic  cavity? 

4.  What  relation  does  the  apex  bear  to  the  chest  wall? 

5.  Can  the  beat  of  the  heart  be  felt  at  any  point  on  the  chest 
wall  and  where? 

6  How  many  surfaces  has  the  heart?    Borders? 

7.  What  are  its  dimensions?    Weight,  male  and  female? 

8.  What  grooves  can  be  seen  on  the  external  surface  of  the  heart 
wall? 

9.  How  many  chambers  has  the  heart? 

10.  AVhat  divides  the  right  side  from  the  left?    The  auricles  from 
the  ventricles? 

11.  How  many  auricles  are  there?    Ventricles? 

12.  What  name  is  given  to  the  opening  between  the  auricle  and 
ventricle? 

13    What  is  the  lining  membrane  of  the  heart  called? 

14.  What  variety  of  cells  are  found  in  the  endocardium? 

15.  What  parts  present  themselves  in  the  right  auricle? 

16.  Name  the  small  muscles  found  in  the  cavities  of  the  right 
and  left  ventricles. 

17.  Name  the  valves  found  in  the  right  and  left  auriculoven- 
tricular  openings.    The  pulmonary  artery  and  aorta. 

18.  How  many  leaflets  has  the  mitral  valve?    Tricuspid  valve? 

19.  What  name   is   given   to   the   cords   extending   between   the 
papillary  muscles  and  margins  of  the  mitral  and  tricuspid  valves? 

20.  Give  a  brief  description  of  the  course  of  the  blood  through 
the  chambers  of  the  heart? 

21.  What  muscle  transmits  the  contraction  wave  of  the  heart 
muscle  from  the  right  auricle  to  the  ventricular  walls? 

22.  How  is  the  cardiac  cycle  divided? 

23.  How  long  does  the  cycle  of  the  heart  last?    How  divided? 

24.  Give  the  normal  beat  of  the  heart  per  minute  in  an  adult. 
Fetus.    First  year  of  life.    Third  year.    Eighth  to  fourteenth  year. 

25.  At  what  point  on  the  chest  wall  can  the  beat  of  the  heart  be 
heard  best? 

26.  What  causes  the  first  sound  of  the  heart?    Second  sound? 

27.  Describe  briefly  the  fetal  circulation. 

28.  Give  the  changes  in  the  fetal  circulation  following  birth. 

29.  Name  the  coats  of  an  artery. 

30.  What  variety  of  tissue  renders  arteries  so  elastic? 

31.  Why  is  the  elasticity  of  the  arterial  wall  so  essential? 

32.  What  causes  arteries  to  contract? 

33.  What  do  you  understand  by  the  term  vasa  vasorum? 

34.  What  are  small  arteries  called?    Veins? 

35.  What  forms  the  walls  of  capillaries? 

36.  What  are  the  functions  of  the  capillaries? 

37.  How  many  coats  form  the  wall  of  a  vein? 

38.  Do  some  veins  possess  valves? 


224  THE  CIRCULATORY  APPARATUS 

39.  What  is  the  pulse? 

40.  Where  is  the  pulse  usually  counted  best? 

41.  What  is  the  pulse  due  to? 

42.  What  do  you  understand  by  a  frequent  or  infrequent  pulse? 
Hard  or  soft?    Tense  or  compressible?    Large,  full,  or  small? 

43.  Define  blood  pressure. 

44.  What  do  you  understand  by  the  term  peripheral  resistance? 

45.  How   can   you    differentiate   a   hemorrhage   from    a  vein   or 
artery? 

46.  What  causes  the  difference  in  character  of  an  arterial  from 
a  venous  hemorrhage? 

47.  What  vessels  carry  the  blood  from  the  right  ventricle  of  the 
heart  to  the  lungs? 

48.  How  does  the  blood  leave  the  left  ventricle  of  the  heart? 

49.  How  does  the  blood  from  the  lungs  reach  the  left  auricle  of 
the  heart? 

50.  What  large  vein  empties  the  systemic  blood  into  the  right 
auricle  of  the  heart? 

51.  What  are  the  divisions  of  the  aorta. 

52.  Name  the  arteries  supplying  the  following  organs:    stomach, 
kidney,  liver,  heart,  lungs,  uterus,  large  bowel,  appendix. 

53.  Give  the  location  of  the  superficial  and  deep  palmar  arches 
in  the  palm  of  the  hand. 

54.  What  are  the  branches  of  the  transverse  arch  of  the  aorta? 

55.  What  veins  form  the  portal  vein? 

56.  Name  the  organs  which  are  drained  by  the  portal  vein  and 
its  tributaries. 

57.  What  is  the  function  of  the  blood? 

58    Is  blood  alkaline  or  acid  in  reaction?     What  is  the  color  of 
arterial  blood?    Venous  blood? 

59.  What   causes   the   red   color   of   arterial   blood?     The   bluish 
color  of  venous  blood? 

60.  What  are  the  constituents  of  blood? 

61.  What  is  the  function  of  fibrinogen  in  blood? 

62.  Is  sugar  found  in  the  blood?    Fat? 

63.  What  are  the  dimensions  of  a  red  cell? 

64.  Describe  the  appearance  of  blood  under  the  microscope. 

65.  What  is  the  function  of  the  hemoglobin  in  the  red  cells? 

66.  What  is  the  normal  average  number  of  red  cells  found  in  one 
cubic  millimeter  of  blood  in  the  male?    Female? 

67.  What  is  the  normal  average  number  of  white  cells  found  in  a 
cubic  millimeter  of  blood? 

68.  What  do  you  understand   by  the  terms  diapedesis,    phago- 
cytosis? 

69.  Describe  the  coagulation  (clotting)  of  blood. 

70.  What  are  the  functions  of  the  white  cells? 


CHAPTER   IX 
THE  LYMPHATIC  SYSTEM 

The  lymphatic  system  includes  primarily  the 
tissues  or  lymph  spaces,  the  lymph  and  blood  capil- 
laries; secondarily,  the  lymphatic  vessels,  and  lymph 
nodes  or  lymphatic  glands,  and  the  veins  which  sub- 
sequently receive  the  lymph  through  the  large  right 
and  thoracic  ducts. 

The  lymphatic  system  is  supposed  to  be  a  closed 
system  in  relation  with  the  tissues.  The  lymph  reaches 
the  lymphatic  vessels  by  transudation  through  the 
endothelial  lining  of  the  vessels;  this  also  occurs  in 
the  serous  membranes,  and  is  not  due  to  the  lymph 
passing  by  permanent  openings  between  the  cells 
(stomata),  as  was  once  held. 

The  Tissues  or  Lymph  Spaces. — These  are  located 
in  practically  every  tissue  and  organ  of  the  body. 
They  are  found  between  cells  (intercellular),  around 
bloodvessels  (perivascular),  and  around  nerves  (peri- 
neural); these  spaces  are  not  lined  by  endothelial 
cells;  the  cells  are  nourished  as  demonstrated  above, 
by  a  transudation  through  the  capillary  walls,  and 
the  lymph  .comes  in  contact  with  the  cells  in  the 
lymph  spaces.  The  spaces  in  the  cranial  cavity,  the 
subdural  and  subarachnoid,  also  the  serous  cavities, 
as  the  pericardial,  pleural,  peritoneal,  and  synovial 
bursse,  are  lined  by  endothelial  cells,  and  the  lymph 
transudes  or  passes  through  the  membranes  by 
osmosis.  The  ventricles  of  the  brain  and  the  central 
canal  of  the  spinal  cord  contain  lymph  from  the  blood 
capillaries  of  these  parts,  and  communicate  with  the 
15 


226  THE  LYMPHATIC  SYSTEM 

subarachnoid  space  (see  Coverings  of  Brain  and  Spinal 
Cord),  whereupon  it  is  taken  up  by  the  lymphatic 
vessels. 

Lymph  Capillaries. — These  are  the  connecting 
vessels  between  the  lymph  spaces  and  the  lymphatic 
vessels  proper.  They  are  thin-walled  vessels,  which 
consist  of  a  single  layer  of  endothelial  cells.  They 
are  arranged  in  plexuses  interwoven  with  the  blood 
capillaries,  and  can  be  easily  distinguished  from  them 
by  their  larger  size  and  irregular  expans?ons. 

The  blood  capillaries,  in  relation  with  the  lymph 
capillaries,  permit  of  a  transudation  of  the  nutritive 
elements  of  the  blood  through  their  thin  walls,  and  at 
the  same  time  assist  in  the  reabsorption  of  a  portion 
of  this  transudate  and  waste  products  resulting  from 
metabolism. 

The  Lymphatic  Vessels. — They  are  arranged  into 
a  superficial  and  deep  set.  The  superficial  set  pass 
just  beneath  the  skin  and  follow  the  course  of  the 
superficial  veins,  some  pierce  the  fascia  to  communi- 
cate with  the  deep  set.  These  drain  the  surfaces  of 
the  head,  neck,  trunk,  and  extremities.  The  deep 
set  follow  the  course  of  the  deeper  bloodvessels,  and 
drain  the  adjacent  tissues.  In  the  interior  of  the 
trunk  the  lymphatics  are  found  in  the  submucous 
layer  of  the  mucous  membrane  of  the  alimentary 
canal  and  respiratory  apparatus,  also  the  genito- 
urinary tract — kidney,  bladder,  etc. 

The  lymphatic  vessels  are  seen  as  a  net-work  of 
minute  vessels,  larger  than  the  capillary  vessels,  in 
the  above-mentioned  tissues  and  organs.  The  lymph 
is  conveyed  through  these  lymph  capillaries  to  larger 
vessels  called  lymphatics,  which  pass  to  small  glandular 
bodies  called  lymph  nodes  or  lymphatic  glands. 

The  deep  lymphatic  vessels  have  the  same  origin 
as  the  superficial  set,  but  are  fewer  in  number  and 
larger.    They  also  drain  into  the  lymph  nodes. 

The  lymph  vessels  are  composed  of  three  coats: 


THE  LYMPHATIC  NODES  227 

The  internal  is  of  elastic  fibers  arranged  lengthwise, 
covered  with  a  layer  of  endothelial  cells;  the  middle 
coat  consists  of  white  fibrous  tissue  arranged  longi- 
tudinally, with  non-striated  muscle  and  elastic  fibers 
arranged  transversely;  the  external  coat  is  practically 
the  same  as  the  middle  coat,  except  that  the  muscle 
fibers  are  arranged  longitudinally. 

Lymph  vessels  possess  valves,  which  are  so  close 
together  and  so  numerous  as  to  appear  as  beads 
upon  the  course  of  the  vessels.  They  face  toward 
the  larger  vessels,  are  arranged  in  pairs,  and  are 
formed  from  a  reduplication  of  the  vessel  wall  rein- 
forced by  white  fibrous  tissue  from  the  middle  coat. 

The  Lymph  Nodes. — They  are  small,  solid,  gland- 
ular bodies  found  along  the  course  of  the  lymphatic 
vessels.  They  vary  in  size  from  a  microscopic 
mass  of  lymphoid  tissue  to  an  olive.  Their  color 
when  cut  is  pinkish,  except  in  the  bronchial  nodes, 
which  are  black,  due  to  the  absorption  of  foreign 
particles  of  dust  from  the  mucous  membranes  of 
the  respiratory  tract;  the  nodes  around  the  liver 
(hepatic)  are  yellowish,  due  to  the  absorption  of  bile 
pigments.    The  splenic  lymph  nodes  are  brown. 

As  the  lymphatic  vessels  from  the  lymph  spaces 
approach  a  node  they  divide  into  numerous  small 
vessels  called  afferent  vessels.  The  latter  pierce  the 
capsule  of  the  gland;  devoid  of  their  outer  coat,  they 
enter  the  sinus  beneath  the  capsule,  termed  the 
subcapsular  sinus,  which  communicates  with  a  central 
sinus.  The  lymph  is  filtered  within  this  node  and  is 
collected  by  small  vessels  which  unite  beneath  the 
capsule  and  pierce  it  as  a  single  efferent  vessel.  Upon 
leaving  the  lymph  node  the  efferent  vessel  is  invested 
by  an  external  coat  derived  from  the  gland  capsule. 
The  lymph  continues  to  pass  on  until  another  set  of 
nodes  are  reached,  when  the  same  arrangement  takes 
place,  and  so  on  until  the  large  lymphatic  vessels 
are  reached,  whereupon,  through  the  thoracic  ducts 


228  THE  LYMPHATIC  SYSTEM 

and  right  lymphatic  duct,  it  is  returned  to  the  venous 
circulation.  While  the  lymph  is  in  the  nodes,  newly 
formed  lymphocytes  attack  and  destroy  any  bacteria 
that  are  present. 

Lymph  nodes  are  divided  into  a  superficial  and 
deep  set,  and  usually  found  around  bloodvessels  and 
embedded  in  fat.  Occasionally  they  are  single,  but,  as 
a  rule,  are  found  arranged  in  chains.  Bloodvessels  and 
nerves  are  plentiful.  Besides  these  nodes,  which  will 
be  classified  and  described  later,  there  are  structures 
allied  to  them — tonsils  and  Beyer's  patches  of  the 
small  intestines. 

The  Composition,  Production,  and  Function  of  Lymph. 
— Lymph  is  a  clear  fluid  found  within  the  tissue  spaces, 
and  termed  intracellular  lymph;  and  in  the  lymphatic 
vessels  called  intravascular  lymph.  It  is  alkaline  in 
reaction,  and  has  a  specific  gravity  of  1.02  to  L04. 
When  observed  under  the  microscope,  numbers  of 
leukocytes  or  white  blood  cells  are  seen.  These  consist 
of  a  small  amount  of  protoplasm  in  which  can  be 
seen  a  nucleus.  Lymph  will  clot,  but  not  as  actively 
or  as  firmly  as  blood.  The  clotting  is  due  to  the 
appearance  of  fibrin. 

The  Chemic  Composition. — This  will  vary,  dependent 
upon  the  portion  of  the  body  drained;  however, 
lymph  obtained  from  the  thoracic  duct  has  been 
found  to  contain,  after  chemic  analysis,  34  to  41 
per  cent,  of  proteins  (serum-albumin,  fibrinogen), 
0.046  to  0.13  per  cent,  of  substances  soluble  in  ether 
(probably  fat),  0.1  per  cent,  of  sugar,  and  from  0.8 
to  0.9  per  cent,  of  inorganic  salts,  of  w^hich  sodium 
chloride  (0.55  per  cent.)  and  sodium  carbonate  (0.24 
per  cent.)  are  the  most  abundant  (Munk).  Small 
amounts  of  calcium,  potassium,  and  magnesium  salts 
are  present;  also  both  free  oxygen  and  carbon  dioxide; 
urea  in  very  small  quantities.  Lymph  is  similar  in 
composition  to  the  plasma  of  the  blood,  only  it  does 
not  contain  any  red  cells. 


FUNCTIONS  OF  THE  INTERCELLULAR  LYMPH     229 

Production  of  Lymph. — ^This  is  still  under  discussion, 
various  theories  being  advanced,  but  none  are  abso- 
lutely definite,  nor  is  any  accepted  by  physiologists  as 
the  correct  one.  It  is  supposed  to  be  formed  by  the 
plasma  of  the  blood  passing  through  the  thin-walled 
capillaries  into  the  small  lymph  spaces  which  exist 
between  the  cells  of  the  adjacent  tissues;  and  another 
theory  is  that  this  transudation  is  aided  by  an  active 
secretory  action  on  the  part  of  the  endothelial  cells 
composing  the  capillary  walls. 

This  passing  or  transudation  of  the  nutritive  material 
and  the  white  cells  through  the  walls  of  the  capillaries 
is  necessary  in  order  to  have  the  tissues  receive  the 
elements  essential  for  their  nourishment,  and  to 
combat,  with  the  contained  lymphocytes,  any  invading 
germ,  or  to  neutralize  any  toxin  within  the  spaces. 
The  passage  of  the  plasma  or  liquid  nutritive  element 
of  the  blood  through  the  capillary  walls  is  based  on 
three  factors:  namely,  osmosis,  diffusion,  and  filtration. 
(See  standard  works  on  physiology.) 

The  Functions  of  the  Intercellular  Lymph. — The 
intimate  contact  of  the  lymph  with  the  tissue  cells 
of  the  body  denotes  that  its  function  is  to  furnish 
those  cells  with  nutritive  elements  essential  to  their 
growth,  repair,  and  functional  activity,  and  to  receive 
from  those  cells  the  products  resulting  from  disintegra- 
tion or  tissue  waste  as  a  result  of  body  metabolism. 

In  order  to  have  the  lymph  in  relation  with  the 
tissue  cells  retain  a  certain  composition,  which  is  con- 
stantly being  reduced  by  the  absorption  of  the  waste 
products  into  the  lymph  vessels  and  blood,  it  is 
necessary  that  the  lymph  be  renewed  as  rapidly  as 
consumed,  and  the  waste  material  removed  as  pro- 
duced. Should  one  of  these  conditions  fail  the  nutri- 
tive elements  of  the  lymph  would  be  reduced,  and 
consequently  destroy  the  vitality  of  the  tissues. 

The  formation  of  lymph  is  a  continuous  phenomena 
and  more  is  formed  than  is  essential  to  the  needs  of 


230 


THE  LYMPHATIC  SYSTEM 


the  tissues  to  maintain  their  normal  activities.    Should 
the  lymph  be  allowed  to  accumulate,  it  would  lead 


Fig.  89 


ASCENDIN 


UPPER  END  OF 
THORACIC  DUCT 


Thoracic  duct,  azygos,  and  intercostal  veins.-    (Testut.) 


THE  THORACIC  DUCTS  231 

to  a  condition  of  edema  and  an  interference  with  the 
functional  activities  of  the  tissues.  But  in  health, 
before  this  condition  of  congestion  is  permitted,  the 
lymphatic  vessels  collect  the  excess  volume  and 
carry  it  into  the  thoracic  ducts,  which  convey  it  into 
the  venous  system.^ 

The  Thoracic  Ducts. — These  are  two  in  number,  the 
right  and  a  common  trunk.  They  drain  all  the  smaller 
lymphatic  vessels  of  the  body  and  open  into  the  veins. 
The  thoracic  duct,  or  common  trunk,  drains  all  the 
vessels  of  the  body,  except  the  right  side  of  the  head 
and  neck,  the  right  upper  extremity,  the  right  side  of 
the  lung  and  its  pleura,  the  heart  and  pericardium,  and 
the  convex  surface  of  the  liver;  the  latter  are  drained 
by  the  right  thoracic  duct.  The  common  trunk  begins 
as  the  receptaculum  chyli,  situated  opposite  the  second 
and  third  lumbar  vertebra  behind  the  peritoneum. 
The  duct  is  15  to  18  inches  in  length.  It  extends  from 
the  second  lumbar  vertebra  to  the  root  of  the  neck, 
where  it  empties  into  the  angle  of  junction  of  the 
subclavian  and  internal  jugular  veins.  It  passes 
through  the  aortic  opening  in  the  diaphragm  between 
the  aorta  and  the  azygos  vein.  In  the  thorax  it  lies 
betw^een  the  esophagus  and  aorta  on  the  thoracic  ver- 
tebra; upon  reaching  the  fourth  thoracic  vertebra  it 
turns  toward  the  left  and  passes  behind  the  arch  of 
the  aorta  and  at  the  seventh  cervical  vertebra  empties 
into  the  veins  as  above. 

The  right  duct  is  only  about  one-half  inch  in  length 
and  opens  into  the  junction  of  the  internal  and  sub- 
clavian veins  in  the  right  side. 


»  The  description  of  the  systemic  lymphatic  vessels  and  glands 
are  not  included,  as  they  are  not  considered  essential  to  a  nurse's 
knowledge. 


232  THE  LYMPHATIC  SYSTEM 


QUESTIONS 

1.  What  structures  are  included  under  the  lymphatic  system? 

2.  How  does  the  lymph  reach  the  lymphatic  vessels? 

3.  Where  are  lymph  spaces  found  in  the  tissues  of  the  body? 

4.  Where  are  the  superficial  set  of  lymphatic  vessels  located? 
Deep  set? 

5.  In  which  layer  of  a  mucous  membrane  are  the  lymphatic 
vessels  usually  found? 

6.  Into  what  structure  does  the  lymphatic  vessel  drain? 

7.  Name  the  coats  of  a  lymphatic  vessel. 

8.  Do  lymph  vessels  possess  valves? 

9.  Describe  a  lymph  node  or  gland. 

10.  What  are  afferent,  efferent  lymphatic  vessels? 

11.  Where  are  lymph  glands  usually  found? 

12.  What  is  the  function  of  a  lymph  capillary? 

13.  What  is  the  relation  and  function  of  blood  capillaries  to  the 
lymph  capillaries? 

14.  Give  the  composition  of  lymph. 

15.  How  is  lymph  produced  generally? 

16.  Is  lymph  a  necessary  fluid  as  regards  the  nourishment  of  the 
tissues? 

17.  What  is  the  function  of  the  thoracic  ducts? 

18.  Where  is  the  receptaculum  chyli  located? 

19.  What  portions  of  the  body  are  drained  of  lymph  by  the  right 
thoracic  duct?    The  left  or  common? 

20.  Into  which  vein  does  the  right  thoracic  duct  empty?     The 
common  duct? 


CHAPTER  X 

THE  RESPIRATORY  APPARATUS 

The  respiratory  apparatus  consists  of  those  organs 
which  receive  and  return  the  air  breathed  through 
the  nose,  mouth,  and  pharynx,  and  convey  it  in  a 
system  of  closed  tubes  and  cavities  to  the  termination 
of  the  lungs,  where  it  comes  in  contact  with  the 
capillaries  of  the  blood,  which  permit,  owing  to  their 
thin  walls  and  the  lining  membrane  of  the  air  cells  of 
the  lungs — a  gaseous  interchange  between  the  carbon 
dioxide  and  other  waste  materials  of  the  blood  and 
the  oxygen  of  the  air  breathed  during  the  act  of 
respiration. 


THE  ORGANS  OF  RESPIRATION 

In  man  the  respiratory  apparatus  is  described 
under  the  following:  Larynx,  Trachea,  Bronchi,  and 
Lungs. 

The  organs  of  respiration  are  located  as  follows: 
The  larynx  and  beginning  of  the  trachea  in  the  neck, 
the  bronchi  and  lungs  within  the  thorax. 

The  Nasal  Cavities. — These  are  the  proper  channels 
for  the  air  to  pass  through.  However,  the  mouth  can 
be  used  as  desired  by  the  individual,  as  is  usually 
employed  by  persons  suffering  from  any  nasal  obstruc- 
tion or  a  deficient  amount  of  air  reaching  the  lungs, 
due  to  heart,  lung,  throat  trouble,  or  changes  in  the 
blood  which  compel  forced  or  labored  breathing — 
dyspnea.     The   air   as   it   passes   through   the   nasal 


234  THE  RESPIRATORY  APPARATUS 

cavities  is  warmed  by  coming  in  contact  with  the 
highly  vascularized  mucous  membrane  lining  them, 
and  thus  is  prevented  from  reaching  the  lungs  at  a 
low  temperature,  which  would  cause  their  congestion 
and  be  dangerous  to  health.  The  air  also  passes 
through  the  pharynx  to  reach  the  larynx. 

The  Larynx. — The  larynx  is  the  organ  of  the  voice, 
and  is  placed  at  the  upper  and  forepart  of  the  neck, 
between  the  trachea  and  base  of  the  tongue.  It  com- 
municates above  with  the  laryngopharynx,  below  with 
the  trachea. 

Relations.— It  has  on  each  side  of  it  the  carotid  vessels, 
and  behind  it  the  pharynx.  In  front  are  the  pretra- 
cheal portions  of  the  cervical  fascia  and  the  upper  end 
of  the  thyroid  gland,  and  on  each  side  the  sterno- 
hyoid and  thyroid  and  the  thyrohyoid  muscles.  It 
consists  of  various  cartilages  held  together  by  liga- 
ments, and  is  lined  internally  by  mucous  membrane, 
continuous  with  that  of  the  pharynx  above  and  the 
trachea  below. 

The  cartilages  are  nine:  Three  pairs,  the  arytenoid, 
cornicula  laryngis,  and  cuneiform;  and  three  single, 
the  thyroid,  cricoid,  and  epiglottis. 

The  thyroid  cartilage  is  the  largest,  and  consists  of 
two  lateral  parts  or  alse  uniting  in  front  to  form  the 
projection  of  the  Adam's  apple  (pomum  Adami). 
This  is  subcutaneous,  more  distinct  above  and  in  the 
male.  Internally  it  is  smooth,  and  in  the  angle  the 
epiglottis,  true  and  false  vocal  cords,  and  the  thyro- 
arytenoid and  thy ro-epiglottidean  muscles  are  attached. 
The  upper  border  is  concavoconvex,  and  in  front  is 
notched  over  the  pomum  Adami,  giving  attachment 
throughout  to  the  thyrohyoid  membrane.  The  lower 
border  is  joined  to  the  cricoid  cartilage  by  the  middle 
portion  of  the  cricothyroid  membrane;  and  on  either 
side,  affords  attachment  to  the  cricothyroid  muscle. 
The  posterior  borders  end  in  the  upper  and  lower 
cornua  (horns);  to  the  upper  are  attached  the  lateral 


THE  ORGANS  OF  RESPIRATION 


235 


thyrohyoid  ligaments,  and  the  lower,  which  are  shorter 
and  thicker,  present  internally  a  facet  for  articulation 
with  the  cricoid  cartilage. 


Fia.  90 


THYROHYOiDEUS 


THYRO-EPIGLOT 
TIC    LIGAMENT 


THYROID 
CARTILAGE 


ARYTENO-EPI- 
GLOTTIOIAN  FOLD 


CRICOID 
CARTILAGE 


Sagittal  section  of  larynx,  right  half.     (Testut.) 


The  cricoid  cartilage  resembles  a  signet  ring,  is 
narrow  in  front,  and  gives  attachment  to  the  crico- 
thyroid muscle,  and  behind  it  to  some  of  the  fibers 
of  the  inferior  constrictor.  It  is  broad  behind,  with 
a  vertical  ridge  for  the  attachment  of  the  longitudinal 
fibers  of  the  esophagus,  and  presents  at  about 
the  middle  of  the  lateral  surface  a  prominence  on 
each  side  which  articulates  with  the  corresponding 


236  THE  RESPIRATORY  APPARATUS 

inferior  cornua  of  the  thyroid  cartilage.  The  lower 
border  is  joined  to  the  upper  ring  of  the  trachea;  the 
upper  border  gives  attachment  in  front  and  laterally 
to  the  cricothyroid  membrane  and  the  lateral  crico- 
arytenoideus  muscle.  Behind,  at  each  end  of  its  upper 
border,  is  an  oval  surface  for  the  corresponding  ary- 
tenoid cartilage,  with  a  notch  between.  The  inner 
surface  is  smooth  and  lined  with  mucous  membrane. 

The  arytenoid  cartilages  are  pyramidal  in  form, 
presenting  three  surfaces,  an  apex,  and  base,  and 
rest  by  their  bases  on  the  highest  part  of  the  upper 
border  of  the  cricoid  cartilage  behind,  their  curved 
apices  approximating. 

The  cornicula  laryngis  (cartilages  of  Santorini)  are  two 
small,  cervical  nodules  of  yellow  elastic  tissue,  which 
articulate  with  the  summits  of  the  arytenoid  cartilages 
and  serve  to  prolong  them  backward  and  inward. 

The  cuneiform  cartilages  (Wrisberg's)  are  two  small, 
yellow  bodies  of  elastic  cartilage,  which  stretch  between 
the  arytenoid  cartilage  and  the  epiglottis. 

The  epiglottis  is  a  fibrocartilaginous  lamella,  shaped 
like  a  leaf,  lying  behind  the  tongue  and  in  front  of 
the  upper  orifice  of  the  larynx.  Above  it  is  broad, 
below  narrow  and  prolonged  to  the  notch  above  the 
pomum  Adami  by  the  thyro-epiglottic  ligament,  or 
rather,  to  the  angular  interval  just  below  the  notch, 
and  is  attached  to  the  upper  border  of  the  body  of  the 
hyoid  bone  by  the  hyo-epiglottic  ligament.  It  falls 
downward  over  the  opening  of  the  larynx  during  the 
swallowing  of  food  to  prevent  the  same  from  entering 
the  larynx. 

The  ligaments  of  the  larynx  are  extrinsic  and  intrinsic. 
The  former  connect  [t  to  the  hyoid  bone;  the  latter 
connect  its  parts  together. 

The  extrinsic  ligaments,  meaning  those  coming 
from  without  or  on  the  outside  of  the  larynx,  are  the 
middle  thyrohyoid  ligament,  the  two  lateral  thyro- 
hyoid ligaments,  and  the  hyo-epiglottic  ligament. 


THE  ORGANS  OF  RESPIRATION  237 

The  intrinsic  ligaments,  meaning  those  within  or 
on  the  inside  of  the  larynx,  connecting  the  thyroid 
and  cricoid  cartilages,  are  the  cricothyroid  membrane, 
two  capsular  ligaments. 

The  cricoid  and  arytenoid  cartilages  are  connected 
by  loose  capsular  ligaments  lined  by  synovial  mem- 
branes, and  by  a  posterior  cricoarytenoid  ligament 
running  from  the  cricoid  to  the  inner  and  back  part 
of  the  base  of  the  arytenoid. 

The  Interior  of  the  Larynx  (Cavum  Laryngis). — This 
is  divided  into  an  upper  and  a  lower  part  by  the  rima 
glottidis.  The  upper  opens  into  the  pharynx  by  the 
upper  aperture  of  the  larynx,  between  which  and  the 
rima  glottidis  are  the  ventricles  and  their  saccules,  and 
the  false  vocal  cords.  The  lower  aperture  is  continuous 
with  the  trachea. 

The  rima  glottidis  is  the  space  between  the  true 
vocal  cords  and  the  bases  of  the  arytenoid  cartilages. 
It  is  somewhat  less  than  1  inch  long,  and  according  to 
its  degree  of  dilatation,  from  J  to  |  inch  wide.  In 
easy  respiration  its  form  is  triangular  with  the  base 
posterior,  and  when  fully  dilated  it  is  lozenge-shaped. 

The  superior  or  false  vocal  cords  are  two  mucous 
folds,  each  enclosing  the  corresponding  superior 
thyro-arytenoid  ligament.  This  latter  is  a  thin  band 
running  between  the  angle  of  the  thyroid  and  the 
antero-external  surface  of  the  arytenoid  cartilage. 

The  inferior  or  true  vocal  cords  are  two  strong  bands, 
the  inferior  thyro-arytenoid  ligaments,  covered  by 
mucous  membrane  and  attached  to  the  depression 
between  the  alse  of  the  thyroid  cartilage  in  front  and 
the  anterior  angle  of  the  base  (vocal  process)  of  the 
arytenoid  cartilages  behind. 

The  ventricles  of  the  larynx  lie  one  on  each  side, 
between  the  upper  and  lower  vocal  cords,  bounded 
externally  by  the  thyro-arytenoidei. 

The  saccule  of  the  larynx  is  a  space  on  each  side, 
between  the  false  vocal  cord  and  the  inner  surface 


238  THE  RESPIRATORY  APPARATUS 

of  the  thyroid  cartilage,  reaching  upward  as  high  as 
the  upper  border  of  that  cartilage,  and  its  mucous 
membrane  presents  the  orifices  of  sixty  or  seventy 
glands.    This  space  has  a  fibrous  capsule. 

The  muscles  of  the  larynx  are  divided  into  extrinsic 
and  intrinsic — the  former  will  be  found  under  the 
muscle  system.    The  latter  are: 

Cricothyroid.  Posterior  crico-arytenoid. 

Thyro-arytenoid.  Lateral  crico-arytenoid. 

Thyro-epiglotticus.       Arytenoid  (single). 

Actions  of  the  intrinsic  muscles:  (1)  Those  which 
open  and  close  the  glottis.  (2)  Those  which  regulate 
the  degree  of  tension  of  the  vocal  cords. 

1.  The  two  posterior  crico-arytenoid s  open  the 
glottis;  and  the  arytenoid  and  the  two  lateral  crico- 
arytenoids close  it. 

2.  The  two  cricothyroids  regulate  the  tension  of 
the  vocal  cords,  and  elongate  them  by  the  same  action; 
the  two  thyro-arytenoid s  relax  and  shorten  them. 

Phonation,  Articulate  Speech.  —  Phonation  is  the 
phenomenon  whereby  the  animal  and  human  being 
are  enabled  to  utter  vocal  sounds,  due  to  the  vibration 
of  two  elastic  membranes,  the  vocal  cords,  which 
cross  the  opening  of  the  larynx  from  before  backward, 
and  which  are  thrown  into  vibration  by  the  air  forced 
from  the  lungs. 

Articulate  speech  is  a  modification  of  the  vocal 
sounds  or  the  voice  produced  by  the  teeth  and  the 
muscles  of  the  lips  and  tongue,  and  is  employed  for 
the  expression  of  ideas  (Brubaker). 

The  Trachea.  —  The  trachea  is  a  membranocar- 
tilaginous  tube,  flattened  behind,  continuous  above 
with  the  larynx,  and  below  dividing  into  the  two 
bronchi. 

The  trachea  consists  of  sixteen  to  twenty  incomplete 
cartilaginous  rings  connected  by  a  fibrous  membrane. 


THE  ORGANS  OF  RESPIRATION  239 

Their  free  ends,  which  are  directed  posteriorly,  are 
united  similarly  and  by  plain  muscular  tissue.  Its 
upper  limit  is  at  the  sixth  cervical,  its  lower,  opposite 
the  body  or  upper  border  of  the  fifth  thoracic  vertebra, 

Fig.  91 


THYROID 
IMPRESSION 


Trachea  and  bronchi,  front  view.     (Testut.) 

and  it  measures  about  41  inches  in  length;  transversely, 
f  to  1  inch.  Its  inner  surface  is  lined  by  a  mucous 
membrane  which  belongs  to  the  stratified,  ciliated 
variety  of  tissues,  and  this  cilia  possesses  a  per- 
petual movement,  carrying  the  particles  of  dust,  etc.. 


240  THE  RESPIRATORY  APPARATUS 

entangled  in  the  mucus  toward  the  entrance  of  the 
respiratory  tract,  where  it  is  expectorated.  The 
submucosa  contains  numbers  of  mucous  glands. 

The  Bronchi. — The  bronchi  enter  the  hilum  of  the 
corresponding  lung.  The  right  is  the  shorter,  wider, 
and  more  horizontal,  and  enters  the  lung  opposite  the 
fifth  thoracic  vertebra,  the  larger  azygos  vein  arching 
over  it  from  behind,  the  right  pulmonary  artery  below 
and  then  in  front  of  it.  The  left  bronchus  is  about 
2  inches  long,  and  enters  the  lung  opposite  the  sixth 
dorsal  vertebra.  It  passes  under  the  arch  of  the  aorta 
and  crosses  in  front  of  the  esophagus,  thoracic  duct, 
and  descending  aorta.  The  left  pulmonary  artery 
lies  at  first  above,  then  in  front  of  it. 

Their  structure  resembles  the  trachea,  only  that 
the  cartilaginous  rings  become  thinner  and  are  replaced 
by  an  increase  in  the  muscular  coat,  as  they  approach 
the  terminal  bronchioles.  The  alveoli,  the  termination 
of  the  bronchioles,  rest  on  a  basement  membrane  of 
elastic  tissue,  surrounded  by  a  capillary  plexus  formed 
by  the  pulmonary  arteries  and  veins. 

The  Pleurae. — The  pleurae  are  two  separate  serous 
sacs  which  invest  each  lung  to  its  root  and  are  reflected 
on  to  the  thoracic  walls  and  pericardium.  That  portion 
of  the  serous  membrane  investing  the  surface  of  the 
lung  and  extending  into  the  fissures  between  the 
lobes  is  called  the  visceral  layer  of  the  pleura  (pleura 
pulmonalis),  while  the  portion  lining  the  inner  surface 
of  the  thorax  is  called  the  parietal  layer  of  the  pleura 
(pleura  parietalis).  The  latter  is  subdivided  into  the 
cervical,  the  costal,  the  diaphragmatic,  and  the 
mediastinal  portions.  The  space  between  the  visceral 
and  parietal  layers  is  the  pleural  cavity  (cavum  pleurae), 
and  contains  a  small  amount  of  clear  fluid.  There  is 
no  cavity  when  the  pleurse  are  in  a  healthy  condition, 
the  two  layers  being  in  contact. 

The  two  pleurse  are  distinct  from  each  other,  and 
do  not  meet  in  the  median  line  except  behind  the 


THE  ORGANS  OF  RESPIRATION 


241 


second  piece  of  the  sternum.  At  the  root  of  the  lung 
the  visceral  and  parietal  layer  of  the  same  side  are 
continuous,  and  at  the  lower  part  of  the  root  a  fold, 
the  ligamentum  latum  piilmonis,  runs  down  to  the 
diaphragm. 


Fig.  92 


TRIANGULARIS    STERN 

Internal  Mammary  Vessels. 


Left  Phrenic  Nerve 


Pleura  Pulmonahs. 
Ptcicra  Costalis. 


St/mpathelic  derive 

Thoracic  Duel. 


Vena  Azygoa  Ma:)or 
Vagus  Nenves 


A  transverse  section  of  the  thorax,  showing  the  relative  positions  of  the 
viscera  and  the  reflections  of  the  pleurae.     (Gray.) 


The  Lungs  (Pulmones) . — The  lungs  are  the  essential 
organs  of  respiration;  they  are  situated  in  the  right 
and  left  sides  of  the  thorax,  covered  by  the  visceral 
portion  of  the  pleura;  filling  the  cavity,  with  the 
exception  of  the  intervening  mediastinum.  The 
latter  is  a  space  within  the  thorax  situated  between 
the  right  and  left  lobes  of  the  lungs;  it  contains  the 
heart  covered  by  the  pericardium,  the  great  vessels 
of  the  heart,  the  esophagus,  trachea,  bronchi,  thymus 
gland,  thoracic  ducts,  nerves  to  the  heart,  lungs,  and 
other  organs.  It  is  divided  into  superior,  anterior, 
16 


242 


THE  RESPIRATORY  APPARATUS 


middle,  and  posterior  portions,  bounded  above  by  the 
root  of  the  neck,  below  by  the  diaphragm.  Each 
lung  presents  for  examination  an  apex,  a  base,  dia- 
phragmatic, costal,  mediastinal  surfaces,  and  anterior, 
posterior,  and  inferior  borders.  It  is  suspended  within 
the  cavity  by  the  root  and  the  ligamentum  pulmonale. 


Fig.  93 


Front  view  of  the  heart  and  lungs.     (Gray.) 


During  respiration  the  lung,  covered  by  the  visceral 
pleura,  is  pressed  again.st  the  walls  of  the  thorax, 
interlined  by  the  parietal  pleura,  and  friction  is  pre- 
vented by  a  small  amount  of  fluid,  within  the  pleural 
cavity,  which  continually  bathes  the  approximating 
surfaces. 


THE  ORGANS  OF  RESPIRATION  243 

The  apex  (apex  pulmonis)  is  rounded,  and  extends 
about  1  inch  to  2  inches  above  the  anterior  end  of 
the  first  rib.  It  is  grooved  by  the  subclavian  artery 
on  the  left  side,  but  on  the  right  side  the  impression  of 
the  innominate  vein  is  the  most  prominent  groove  seen. 

Fissures  and  Lobes. — The  left  lung  is  divided  into 
two  lobes,  an  upper  and  a  lower,  by  an  oblique  fissure, 
which  extends  from  the  outer  to  the  inner  surface  of 
the  lung  both  above  and  below  the  hilum.  The  right 
lung  is  divided  into  three  lobes,  an  upper,  middle, 
and  lower,  by  an  oblique  fissure,  separating  the  lower 
and  middle  lobes,  a  horizontal  fissure  separating  the 
upper  and  middle  lobes. 

The  Root  of  the  Lung  (Radix  Pulmonis). — This  lies 
a  little  above  the  centre  of  the  mediastinal  surface, 
and  approaches  nearer  to  the  posterior  than  to  the 
anterior  border.  It  transmits  the  bronchus,  the 
pulmonary  artery,  the  two  pulmonary  veins,  usually 
the  bronchial  arteries  and  veins — the  former  supply 
the  bronchi  and  lungs  with  blood — the  pulmonary 
plexus  of  .nerves,  lymphatics,  the  bronchial  lymph 
nodes,  and  areolar  tissue,  surrounded  by  a  reflection 
of  the  pleura  which  fuses  with  the  pericardium  at 
this  point. 

Structure  of  the  Lungs. — The  color  of  the  lungs  at 
birth  is  a  pinkish  white;  in  adult  life,  a  dark  slate 
color,  mottled  in  patches;  and  as  age  advances  this 
assumes  a  black  color. 

The  lungs  are  composed  of  an  external  serous  coat, 
subserous  areolar  tissue,  and  parenchyma,  consisting 
of  numbers  of  lobules  (|  to  1^  inches  in  size).  The 
structures  enclosed  within  the  lungs  consist  of  bronchi, 
their  subdivisions  which  end  in  the  air  cells,  blood- 
vessels, lymphatics  and  nerves,  all  embedded  in  a  sup- 
porting net-work  of  fibrous  and  elastic  tissue.  These 
structures  can  only  be  seen  under  the  microscope. 

The  bronchi,  on  passing  to  the  periphery  of  the 
lung,  become  smaller  and  smaller  as  they  divide  and 


244  THE  RESPIRATORY  APPARATUS 

subdivide.  The  walls  become  thinner  and  the  car- 
tilaginous rings  disappear.  The  smallest  bronchial 
tubes  contain  muscle  tissue  in  their  walls.  These 
latter  fibers,  when  stimulated  by  nerves  from  the 
vagus,  cause  a  narrowing  of  the  caliber  of  the  bronchial 
tubes.  When  the  bronchial  tubes  are  so  reduced 
as  to  measure  about  1  millimeter,  they  are  termed 
bronchioles.  From  the  latter  are  given  off  small 
branches  which  soon  expand  to  form  numbers  of 
lobules  or  alveoli.  The  central  space  of  the  alveoli  is 
called  the  infundibulum,  and  from  the  inner  surface 
of  the  alveolus,  project  small  partitions  which  include 
the  air  sacs  or  cells  between  them.  The  walls  of  the 
alveolus  are  very  thin  and  composed  of  fibro-elastic 
tissue.  The  bronchi  and  bronchioles  are  lined  with 
ciliated  epithelium  and  the  alveoli  and  air  cells  by 
flat  epithelial  cells,  called  respiratory  epithelium. 

The  bronchi  and  their  subdivisions  are  accompanied 
by  branches  of  the  pulmonary  artery,  and  pulmonary 
and  bronchial  veins.  The  pulmonary  arteries  upon 
reaching  the  alveoli  of  the  lungs  form  a  capillary  net- 
work which  is  in  intimate  relation  with  the  respiratory 
epithelium  of  the  air  sacs,  only  the  thin  wall  of  the 
capillary  intervening.  This  permits  of  the  ready  inter- 
change of  the  carbon  dioxide  through  the  wall  of  the 
capillary  and  respiratory  epithelium  with  the  intrapul- 
monary  air,  and  the  oxygen  from  the  latter  is  absorbed 
in  the  same  way  by  the  red  cells  of  the  blood  in  the  pul- 
monary capillaries,  and  returned  to  the  left  side  of  the 
heart.  The  bronchial  arteries  supply  the  walls  of  the 
larger  bronchial  tubes  and  tissue  of  the  lungs  anasto- 
mosing with  the  capillaries  of  the  bronchial  and  pulmo- 
nary veins.  The  bronchial  veins  pass  back  to  empty 
into  the  azygos  system  on  the  right  side  and  on  the 
left  they  drain  into  the  superior  intercostal  vein.  The 
pulmonary  veins  are  supposed  to  contain  some  venous 
blood  derived  from  the  bronchial  venous  capillaries, 
besides  their  arterial  blood. 


RESPIRATION  245 


RESPIRATION 


Respiration  is  a  process  whereby  the  lungs  receive 
the  oxygen  from  the  air  we  breathe;  it  is  carried  to 
the  tissues  by  the  hemoglobin  of  the  red  cells,  where  it 
is  given  off  to  the  tissues;  carbon  dioxide  is  taken  up 
by  the  hemoglobin  from  the  tissues  and  carried  by  the 
red  cells  to  the  lungs,  where  it  is  given  off  in  the  expired 
air.  Respiration,  therefore,  is  a  function  indispensable 
to  life  and  plays  a  most  important  part  in  the  main- 
tenance of  body  metabolism,  by  supplying  oxygen  to 
the  tissues,  and  removing  carbon  dioxide  from  the 
tissues  in  the  chemic  interchange  taking  place  between 
the  air,  the  blood,  and  the  tissues  during  the  act  of 
respiration,  and  circulation  of  the  blood. 

Rate  of  Respiration. — The  normal  rate  of  respira- 
ation  varies  at  different  ages  as  follows:  At  birth  and 
during  the  first  year,  44  per  minute;  five  years,  26  per 
minute;  fifteen  to  twenty  years,  20  per  minute;  twenty 
to  twenty-five  years,  18.7  per  minute;  thirty  to  fifty 
years,  18  per  minute. 

Respiration  is  divided  into:  inspiration,  an  active 
process  due  to  muscular  activity,  when  air  enters  the 
lungs,  due  to  atmospheric  pressure  being  greater 
than  the  contained  intrapulmonary;  expiration,  a  quiet 
or  passive  process,  due  to  the  recoil  of  the  elastic 
tissue  of  the  lungs,  the  abdominal  and  thoracic  walls; 
when  the  intrathoracic  pressure  becomes  greater  than 
the  atmospheric  air  pressure  it  allows  the  contained 
air  to  escape  until  the  intrapulmonary  pressure  equals 
the  atmospheric  air  pressure,  then  inspiration  occurs 
again,  and  the  respiratory  cycle  is  repeated. 

The  Volumes  of  Air  Breathed. — This  is  determined 
by  an  apparatus  known  as  Hutchinson's  spirometer. 
With  this  apparatus  four  volumes  of  air  are  deter- 
mined. (1)  The  tidal  volume  or  the  amount  of  air 
which  flows  into  and  ou^  of  the  lungs  during  an  ordinary 


246  THE  RESPIRATORY  APPARATUS 

inspiration  and  expiration  varies  from  20  to  30  cubic 
inches.  (2)  The  complemental  volume  or  the  amount 
of  air  taken  into  the  lungs,  in  addition  to  the  tidal 
volume,  resulting  from  a  forcible  inspiration,  which 
amounts  to  110  cubic  inches.  (3)  The  reserve  volume 
or  the  amount  of  air  which  flows  out  of  the  lungs,  in 
addition  to  the  tidal  volume  resulting  from  a  forcible 
expiration,  which  amounts  to  100  cubic  inches.  (4) 
The  residual  volume  or  amount  of  air  remaining  in  the 
lungs,  as  a  permanent  volume,  after  the  most  forcible 
expiration. 

The  vital  capacity  is  the  amount  of  air  which  can 
be  expelled  from  the  lungs  after  they  are  filled  by  the 
most  forcible  inspiration.  This  amounts  to  230  cubic 
inches  (3593  c.c).    * 

Changes  in  the  Composition  of  Inspired  and  Expired 
Air  as  a  Result  of  Respiration. 

Inspired  Air,  100  Volumes 

Oxygen 20.80 

Carbon  dioxide traces 

Nitrogen 79.20 

Watery  vapor variable 

Expired  Air,   100  Volumes 

Oxygen 16.02 

Carbon  dioxide 4.38 

Nitrogen 79.60 

Water  vapor saturated 

Organic  matter  (Brubaker) 

The  above  analyses  show  that  the  air  under  ordinary 
conditions  loses  oxygen  to  the  extent  of  4.37  per  cent., 
and  gains  in  carbon  dioxide  to  the  extent  of  4.38  per 
cent.;  it  gains  in  nitrogen  to  the  extent  of  0.4  per  cent., 
and  watery  vapor  to  the  point  of  saturation,  also 
organic  matter. 

From  experiments  with  the  spirometric  apparatus, 
and  the  taking  of  the  percentage  loss  of  oxygen  and 
gain  in  carbon  dioxide  shown  by  the  analysis  of  the 


RESPIRATION  247 

respired  air,  it  is  possible  to  figure  approximately 
the  total  amount  of  oxygen  absorbed  and  carbon 
dioxide  given  off  during  respiration.  The  minimum 
daily  volume  of  air  breathed  is  assumed  to  be  10,800 
liters  and  the  maximum  daily  volume  12,240  liters. 
Thus  the  minimum  daily  yolume  of  oxygen  absorbed 
is  510  liters,  maximum  585  liters.  Carbon  dioxide 
is  exhaled  amounting  to  473  liters,  the  minimum 
daily  volume;  526  liters,  the  maximum  daily  volume. 

Thus  one  can  readily  understand  how  essential  it 
is  for  human  beings  to  obtain  a  fresh  supply  of  air 
to  breathe  in  order  to  maintain  life  and  carry  on  its 
various  activities.  Since  during  every  breath  the 
external  air  loses  oxygen  and  gains  carbon  dioxide, 
besides  other  waste  products,  the  air  in  dwellings, 
offices,  etc.,  should  be  frequently  renewed  in  order 
to  maintain  a  condition  of  health.  If  we  take  in  at 
each  inspiration  30  cubic  feet  of  air,  and  breathe  at 
the  rate  of  18  respirations  a  minute,  then  in  twenty- 
four  hours  450  cubic  feet  (12.8  cm.)  will  pass  in  and 
out  of  the  lungs.  Thus  it  is  easy  to  understand  how 
a  person  laboring,  or  sleeping,  etc.,  in  an  unventilated 
room  w^ould  readily  succumb,  theoretically,  by  rebrea th- 
ing the  poisoned  air  from  his  own  lungs. 

The  Changes  in  the  Blood  during  Respiration.— 
The  blood  as  it  is  forced  from  the  right  ventricle  of 
the  heart  through  the  pulmonary  artery  to  the  lungs, 
is  dark  bluish  red  in  color.  On  reaching  the  air  cells 
of  the  lungs  the  blood  becomes  bright  red  in  color  and 
is  carried  through  the  pulmonary  veins  to  the  left 
auricle,  then  into  the  left  ventricle  of  the  heart,  when 
it  passes  out  through  the  large  artery  (aorta)  to  supply 
the  body  tissues. 

The  blood  is  changed  while  flowing  through  the 
capillaries  from  fhe  venous  to  the  arterial  state.  When 
the  dark  bluish-red  blood  in  the  pulmonary  arteries 
reaches  the  capillaries  of  the  pulmonary  system  where 
they  surround  the  air  cells,  and  the  thin  membrane 


248  THE  RESPIRATORY  APPARATUS 

separating  the  capillaries  from  the  intrapulmonary 
air,  the  carbon  dioxide  is  given  off  and  the  oxygen  is 
taken  up  and  combines  chemically  with  the  hemo- 
globin contained  in  the  red  cells,  forming  oxyhemo- 
globin, the  blood  in  the  arterial  capillaries  of  the 
pulmonary  veins  immediately  turns  bright  red  as  a 
result  of  the  interchange.  This  bright  red  or  arterial 
blood  is  carried  to  the  tissues  by  the  arteries  and 
capillaries. 

Fig.  94 


AIR 

THIN  MUCOSA 

l-1-l-l-l'l'l-l- 

CAPILLARY  BLOOD  VESSEL 

(®  ©(S>0©©©C2)  O  03a©(20  O0G)©  ©  <2© 

Diagram  of  the  essentials  of  a  respiratory  apparatus.     (F.  H.  G.) 

This  power  possessed  by  the  blood  of  absorbing 
and  giving  up  oxygen  and  carbon  dioxide  through  the 
capillary  walls  from  and  to  the  air  and  tissues  respec- 
tively is  based  on  the  well-known  fact  that  liquids 
will  absorb  or  dissolve  at  any  constant  pressure 
unequal  volumes  of  different  gases  in  accordance  with 
their  solubilities,  and  with  variations  in  temperature 
(Brubaker) . 

The  Relation  of  the  Nerve  System  to  Respiration. — 
The  rhythmic  movements  of  respiration  are  controlled 
by  nerve  impulses  which  arise  in  groups  of  nerve  cells 
in  the  central  nerve  system,  and  are  transmitted  to 
the  inspiratory  and  expiratory  centres  in  the  medulla 
oblongata,  which  are  stimulated  into  activity. 

The  inspiratory  and  expiratory  centres  are  included 
under  the  term  respiratory  centre. 

The  vagus  nerve  is  the  important  nerve  which 
transmits  nerve  impulses  from  the  inspiratory  centre 
in  the  medulla  to  the  lungs.  It  contains  excitor  and 
inhibitor  fibers;  the  former,  when  stimulated,  increase 
the  rate  of  inspiration  and  the  latter  decrease  it. 


QUESTIONS  249 

Respiration  is  believed  to  be  due  to  a  stimulus 
resulting  from  the  alternate  distention  and  collapse 
of  the  walls  *  of  the  pulmonary  alveoli — a  mechanic 
action. 

The  inspiratory  centre  can  be  influenced  directly 
by  nerve  impulses  being  transmitted  from  the  brain 
in  response  to  voluntary  acts,  or  emotional  states, 
sighing,  etc.,  also  indirectly  by  nerve  impulses  reflected 
to  the  centre  from  the  surfaces  of  the  skin  and  mucous 
membranes  through  afferent  nerves;  as  cold  applied 
to  the  skin,  irritating  gases  to  the  nasal  and  bronchial 
mucous  membranes,  and  collapse  or  distention  of  the 
pulmonary  alveoli. 


QUESTIONS 

1.  Name  the  organs  of  respiration. 

2.  What  effect  has  the  nasal  mucous  membranes  upon  the  air 
we  breathe? 

3.  What  is  dyspnea? 

4.  What  is  the  organ  of  the  voice? 

5.  Give  the  relations  of  the  larynx. 

6.  How  many  cartilages  form  the  larynx?    Name  them. 

7.  Which  cartilage  forms  the  Adam's  apple? 

8.  What  is  the  rima  glottidis? 

9.  Describe  the  true  and  false  vocal  cords. 

10.  Which  muscles  open  the  glottis?    Close  it? 

11.  Which  muscles  regulate  the  tension  of  the  vocal  cords?    Relax 
them? 

12.  What  do  you  understand  by  the  term  phonation? 

13.  How  is  articulate  speech  produced? 

14.  Name  the  number  of  rings  in  the  trachea. 

15.  What  variety  of  epithelium  lines  the  trachea  and  what  is  its 
function? 

16.  Are  there  glands  in  the  trachea,  and  to  what  variety  do  they 
belong? 

17.  Where  do  the  bronchi  enter  the  lungs? 

18.  Are  the  pleurae  closed  sacs? 

19.  What  do  you  understand  by  the  terms  visceral  and  parietal 
pleura? 

20.  Where  is  the  pleural  cavity  located?    Does  it  contain  fluid? 

21.  What  membranes  cover  the  lung? 

22.  Name  the  parts  of  each  lung. 

23.  What  structures  form  the  root  of  the  lung?* 

24.  How  many  lobes  has  the  right  lung?    The  left? 

25.  Give  the  microscopic  structure  of  the  lung. 


250  THE  RESPIRATORY  APPARATUS 

26.  What  is  a  bronchiole?    Lobule? 

27.  Where  is  the  infundibulum  in  the  lobules  of  the  lungs?  The 
air  sacs? 

28.  Name  the  variety  of  epithelium  lining  the  bronchi,  bronchioles, 
alveoli,  and  air  sacs. 

29.  What  relation  do  the  capillaries  of  the  pulmonary  artery  and 
vein  bear  to  the  air  sacs  of  the  lobules? 

30.  What  relation  do  the  respiratory  epithelium  and  capillaries 
bear  to  respiration? 

31  Describe  respiration. 

32.  Give  the  normal  rate  of  respiration  per  minute  at  birth.  Five 
years.  Fifteen  to  twenty  years.  Twenty  to  twenty-five  years. 
Thirty  to  fifty  years. 

33.  Name  the  divisions  of  respiration. 

34.  What  do  you  understand  by  the  terms  tidal  volume?  comple- 
mental  volume?  reserve  volume?  residual  volume?  in  relation  to 
respiration? 

35.  What  is  the  average  vital  capacity  of  the  lungs?  What  is 
meant  by  it? 

36.  Give  the  minimum  and  maximum  daily  volume  of  air  breathed. 

37.  What  gaseous  interchange  takes  place  during  each  respiration 
between  the  hemoglobin  of  the  red  cells  and  the  air  we  breathe? 

38.  How  is  the  color  of  the  blood  affected  by  respiration? 

39.  Where  is  the  oxygen  absorbed  at  each  respiration  carried  to? 
Where  does  the  carbon  dioxide  in  the  blood  come  from  to  be  given 
off  at  each  respiration? 

40.  What  centre  in  the  medulla  controls  inspiration  and  expira- 
tion? 


CHAPTER  XI 
THE  ORGANS  OF  DIGESTION 

The  digestive  apparatus  for  the  digestion  of  the  food 
we  eat  consists  of  the  alimentary  canal  and  accessory 
organs. 

The  alimentary  canal  is  a  musculomembranous 
tube,  about  thirty  feet  in  length,  extending  from  the 
mouth  to  the  anus,  and  lined  by  mucous  membrane 
throughout  the  entire  length. 

It  is  divided  in  different  parts  according  to  the 
mechanical  or  chemical  changes  taking  place  during 
the  various  stages  of  digestion:  as  the  mouth,  where 
the  teeth,  tongue,  and  salivary  glands  perform  the  act 
of  mastication  and  insalivation;  the  pharynx  and 
esophagus,  which  receive,  force,  and  convey  the  food 
to  the  stomach,  as  in  the  act  of  swallowing  or  degluti- 
tion; the  stomach,  in  which  the  chief  chemical  changes 
occur  and  the  food  is  reduced  to  a  semiliquid  condition, 
to  be  passed  on  to  the  small  intestines;  the  small 
intestines,  where  it  is  acted  upon  by  the  bile,  pan- 
creatic and  intestinal  juices  which  separate  and 
render  absorbable  the  nutritive  material;  the  large 
intestines,  to  which  that  portion  of  the  food  which 
is  unabsorbable  moves  on  to  pass  out  through  the 
rectum  and  anus  as  feces  or  waste  particles. 

The  accessory  organs  of  digestion  are:  the  teeth, 
tongue,  salivary  glands — parotid,  submaxillary,  and 
sublingual — the  liver  and  pancreas. 


252  THE  ORGANS  OF  DIGESTION 

The  alimentary  canal  consists  of  the  following: 

Mouth.  [Duodenum. 

Pharynx.  Small  Intestine    j. Jejunum. 

Esophagus.  Uleum. 

Stomach .  f  Cecum . 

Colon. 

Rectum. 

Anal  canal. 


Large  Intestine 


THE  MOUTH,  ORAL  OR  BUCCAL  CAVITY 

The  mouth  is  the  upper  part  of  the  alimentary  canal. 
It  is  bounded  by  the  lips,  cheeks,  tongue,  hard  and 
soft  palate,  alveolar  processes  of  both  jaws,  with 
their  contained  teeth,  and  opens  behind,  through  the 
isthmus  faucium,  into  the  pharynx.  It  is  lined  by 
mucous  membrane  continuous  in  front  with  the  skin, 
behind  with  that  of  the  fauces,  its  epithelium  being 
stratified. 

The  Teeth. — The  teeth  in  the  human  subject  are 
erupted  in  two  sets,  a  temporary  or  deciduous,  or  milk 
teeth,  and  a  permanent  or  succedaneous  set.  The 
former  are  20  in  number,  10  in  each  jaw;  the  latter, 
32,  16  each  above  and  below.  Each  tooth  is  made 
up  of  three  parts:  the  root,  consisting  of  one  or  more 
fangs,  contained  in  the  alveolus;  the  crown  or  body, 
above  the  gum;  and  the  neck,  between  the  two.  The 
alveolar  periosteum  is  reflected  on  to  the  fang  as  far 
as  the  neck. 

The  twenty  temporary  teeth  are  divided  into  4  inci- 
sors, 2  canines,  and  4  molars  above  and  below.  The  32 
permanent  teeth  are :  4  incisors,  2  canines,  4  bicuspids, 
and  6  molars  in  each  jaw.  The  temporary  teeth  are 
similar  to  but  smaller  than  the  permanent;  of  the 
temporary  molars,  the  hinder  one  is  the  largest  of 


THE  MOUTH,  ORAL  OR  BUCCAL  CAVITY     253 

all,  and  its  place  is  afterward  taken  by  the  second 
permanent  bicuspid. 

Of  the  permanent  teeth  the  incisors  are  the  8  central 
cutting  teeth,  4  each  above  and  below,  the  former 
being  the  larger.  They  are  bevelled  at  the  expense 
of  the  posterior  surface.  The  canines  (cuspidati)  are 
2  in  each  jaw,  being  situated  1  behind  each  lateral 
incisor,  the  upper  and  larger  being  called  the  eye 
teeth.     The   bicuspids    (premolars  or  false   molars), 

4  in  each  jaw,  lie  2  each  behind  the  canines,  the  upper 
being  the  larger.  The  molars  {true  molars  or  multi- 
cuspidati)  are  the  largest  teeth,  and  number  6  in 
each  jaw,  3  each  behind  the  posterior  bicuspids  above 
and  below.    They  present  4  tubercles  on  the  upper, 

5  on  the  lower  crowns,  and  the  root  is  subdivided  into 
from  2  to  5  fangs.  The  first  molar  is  the  largest  and 
broadest,  the  second  smaller,  and  the  third  (wisdom 
tooth)  the  smallest. 

Fig.  95 


Pulp  Cavity. 


Vertical  section  of  molar  tooth. 

A  vertical  section  of  a  tooth  shows  it  to  be  hollow, 
the  cavity  being  continuous  with  the  aperture  in  the 
fang  and  filled  up  with  the  soft  dental  pulp,  and  is 
hence  called  the  pulp  cavity.  The  pulp  is  sensitive, 
highly  vascular,  and  consists  of  connective  tissue, 
with  cells,  vessels,  and  nerves.  The  hard  substance 
of  each  tooth  consists  of  three  parts:  the  ivory  or 
dentin,  the  enamel,  and  the  crusta  petrosa  or  cement. 


254  THE  ORGANS  OF  DIGESTION 

The  period  of  eruption  of  the  temporary  teeth  are 
(C.  S.  Tome): 

Lower  central  incisors 6  to    9  months 

Upper  incisors 8  to  10  months 

Lower  lateral  incisors  and  first  molars  .  15  to  21  months 

Canines 16  to  20  months 

Second  molars 20  to  24  months 

The  period  of  eruption  of  the  permanent  teeth  are  : 

First  molars 65  years 

Two  middle  incisors 7th  year 

Two  lateral  incisors 8th  year 

First  bicuspid 9th  year 

Second  bicuspid 10th  year 

Canine 11th  to  12th  year 

Second  molars 12th  to  13th  year 

Third  molars 17th  to  21st  year 

The  Tongue  (Lingua). — The  tongue  is  the  organ  of  the 
special  sense  of  taste/  also  assisting  in  insalivation,  mas- 
tication, deglution,  and  articulate  speech.  It  is  situated 
in  the  floor  of  the  mouth,  in  the  interval  between  the 
horizontal  rami  of  the  mandible.  It  is  attached  to  the 
hyoid  bone  at  the  base  by  the  genioglossus  and  hyo- 
glossus  muscles  and  the  hyoglossal  membrane;  with  the 
epiglottis  by  three  folds,  the  glosso-epiglottic  folds,  of 
mucous  membrane;  with  the  soft  palate  by  means 
of  the  anterior  pillars  of  the  fauces;  and  with  the 
pharynx  by  the  superior  constrictor  muscles  and  the 
mucous  membrane. 

The  muscles  controlling  the  tongue  are  the  extrinsic, 
which  are  inserted  into  the  tongue,  their  terminal 
fibers  contained  wathin  the  substance,  namely,  the 
styloglossus,  the  hyoglossus,  the  palatoglossus,  the 
genioglossus,  and  part  of  the  superior  constrictor  of 
the  pharynx  (pharyngoglossus) .  The  intrinsic  muscles 
of  the  tongue  are :  the  superior  lingualis,  the  chondro- 
glossus,  the  transverse  lingualis,  the  vertical  lingualis, 
and  the  inferior  lingualis. 

*  See  chapter  Sense  of  T^istc,  page  406. 


THE  MOUTH,  ORAL  OR  BUCCAL  CAVITY     255 

The  arteries  of  the  tongue  are  derived  from  the 
lingual,  the  facial,  ascending  pharyngeal  (all  branches 
of  the  external  carotid  artery).  The  veins  open  into 
the  internal  jugular.    The  lymphatic  vessels  from  the 


Fig.  96 

UVULA 


PHARYNX 


I  CIRCUM- 
VALLATE 
PAPILL/E 


Doraal  surface  of  the  tongue.     (Teatut.) 


256  THE  ORGANS  OF  DIGESTION 

anterior  half  of  the  tongue  drain  into  the  submaxillary 
nodes.  Those  draining  the  posterior  half  end  in  the 
deep  cervical  nodes;  along  the  internal  jugular  vein. 

Nerves  of  Tongue. — (See  Nerve  System,  pages  374 
and  406.) 

The, Palate. — The  palate  forms  the  roof  of  the 
mouth,  and  consists  of  a  front  part  or  hard,  and  a 
back  part  or  soft  palate.  The  periosteum  of  the  hard 
palate  (see  Bones)  is  covered  by  and  intimately  con- 
nected with  the  mucous  membrane  of  the  mouth. 
In  the  middle  line  is  a  raphe  ending  in  front  at  a 
small  papilla,  which  marks  the  anterior  palatine  fossa 
which  receives  the  terminal  part  of  the  anterior 
palatine  and  nasopalatine  nerves.  The  mucous  mem- 
brane is  pale  and  corrugated,  covered  with  squamous 
epithelium,  and  furnished  with  a  number  of  palatal 
glands  which  lie  between  it  and  the  bone. 

The  soft  palate  partially  separates  the  mouth  and 
pharynx.  It  consists  of  muscular,  connective,  and 
adenoid  tissue,  with  vessels,  nerves,  and  mucous 
glands,  all  enclosed  in  a  fold  of  mucous  membrane. 
Above  it  is  joined  to  the  back  of  the  hard  palate; 
laterally  it  blends  with  the  pharynx;  below  it  is  free; 
in  front  it  is  concave,  with  a  median  ridge;  and  behind 
it  is  convex.  Its  mucous  membrane  is  continuous  with 
that  of  the  roof  of  the  mouth  and  of  the  posterior  nares. 

From  its  lower  border  a  conical  process  depends, 
the  uvulaj  from  whose  base  descend  the  pillars  of  the 
soft  palate,  the  anterior,  formed  by  the  palatoglossi 
muscles,  to  the  sides  of  the  base  of  the  tongue;  the 
posterior,  formed  by  the  palatopharyngei,  to  the  sides 
of  the  pharynx.  These  pillars  are  covered  by  mucous 
membrane  and  separated  below  by  the  tonsil,  the 
space  being  called  the  isthmus  of  the  fauces. 

The  tonsils  (tonsilla  palatina)  are  two  in  number, 
situated  on  each  side  of  the  fauces,  and  lie  between 
the  anterior  and  posterior  palatine  pillars,  and  are 
about  J  inch  long  and  \  inch  wide  and  thick,  but  vary 
much  in  size. 


THE  MOUTH,  ORAL  OR  BUCCAL  CAVITY     257 

The  Salivary  Glands. — There  are  three  pairs, 
parotid,  submaxillary,  and  sublingual. 

The  parotid  gland,  the  largest,  weighs  J  to  1  ounce, 
and  lies  on  the  face  below  and  in  front  of  the  ear.  Its 
outer  surface,  lobulated,  is  covered  by  the  skin  and 
fascia,  and  partly  by  the  platysma  and  several  lym- 
phatic glands. 


Fig.  97 


The  salivary  glands.     (Gray.) 


The  duct  (Stenson's)  is  about  2J  inches  long  and  \ 
inch  in  diameter,  and  opens  opposite  the  second 
molar  tooth,  into  the  mouth,  thence  runs  backward 
beneath  the  mucous  membrane,  through  the  buccina- 
tor, and  across  the  masseter  to  the  front  of  the  gland. 
It  conveys  the  saliva  to  the  mouth. 

The  submaxillary  gland  is  of  an  irregular  form,  weighs 
about  2  drams,  and  lies  below  the  jaw^  and  above  the 
17 


258  THE  ORGANS  OF  DIGESTION 

digastric  muscle.  It  is  covered  by  the  skin,  platysma, 
and  fasciae,  and  grooves  the  inner  surface  of  the  lower 
jaw. 

The  submaxillary  duct  (Wharton's)  is  2  inches  long, 
and  opens  at  the  top  of  a  papilla  close  to  the  frenum 
of  the  tongue  into  the  mouth.  Thence  it  runs  back 
between  the  sublingual  gland  and  the  geniohyoglossus, 
then  between  the  mylohyoid  and  the  hyoglossus  and 
geniohyoglossus. 

The  sublingual  gland,  the  smallest  of  the  salivary 
glands,  lies  at  the  side  of  the  frenum  of  the  tongue 
and  against  the  inner  surface  of  the  lower  jaw,  beneath 
the  mucous  membrane.  It  is  almond-shaped,  weighs 
1  dram,  and  its  ducts  (of  Rimii),  ten  to  twenty  in 
number,  open  separately,  one  or  two  joining  to  form 
the  duct  of  Bartholin,  which  joins  Wharton's  duct. 


THE   PHARYNX 

The  pharynx  is  a  musculomembranous  tube,  conical 
in  shape,  between  the  oral  cavity  and  the  esophagus; 
communicating  with  the  posterior  nares,  the  oral 
cavity,  the  larynx,  the  two  Eustachian  tubes.  It  is 
attached  above  to  the  periosteum  of  the  petrous 
portion  of  the  temporal  bone  and  the  basilar  process 
of  the  occipital  bone.  The  raphe  of  the  constrictor 
muscles  is  attached  to  the  pharyngeal  tubercle  of  the 
basilar  process  of  the  occipital  bone.  It  is  bounded 
above  by  the  body  of  the  sphenoid  and  basilar  process 
of  the  occipital;  below,  it  is  continuous  with  the 
esophagus;  anteriorly,  it  is  incomplete,  and  is  attached 
to  the  Eustachian  tube,  the  internal  pterygoid  plate, 
the  pterygomandibular  ligament,  the  posterior  portion 
of  the  mylohyoid  ridge,  the  mucous  membrane  of 
the  mouth,  the  base  of  the  tongue,  the  hyoid  bone, 
the  thyroid  and  cricoid  cartilages;  posteriorly,  the 
prevertebral  fascia,  and  areolar  tissue   connect  it  to 


THE  PHARYNX 


259 


the  cervical  portion  of  the  vertebral  column,  anterior 
to  the  longus  colli  and  rectus  capitis  anticus  muscles, 
the  areolar  tissue  is  contained  in  the  retropharyngeal 


Fig.  98 


Sagittal  section  of  face  and  neck,  showing  external  wall  of  right 
nasal  fossa.     (Testut.) 


space;  laterally,  it  is  connected  to  the  styloid  process 
and  its  muscles.  The  constrictor  muscles  surround  it 
and  aid  in  deglutition.     It  is  4 J  inches  long,  and  for 


260  THE  ORGANS  OF  DIGESTION 

purposes  of  studying,  divided  into  a  nasal,  oral,  and 
laryngeal  portion. 

The  nasal  part  or  nasopharynx,  lies  posterior  to  the 
nares  and  above  the  soft  palate*  In  front  are  the 
posterior  nares  (choanse);  behind,  the  pharyngeal 
tonsil,  consisting  of  lymphoid  tissue  seen  above  the 
orifices  of  the  Eustachian  tubes  in  the  median  hne. 
The  floor  of  the  nasopharynx  is  continuous  with  the 
nasal  fossae,  anteriorly,  and  behind  is  the  sloping 
portion  of  the  soft  palate.  On  its  lateral  wall  is  the 
orifice  of  the  Eustachian  tube,  level  with  the  inferior 
turbinated  bone  and  one-third  to  one-half  inch  pos- 
terior. 

The  oral  part  extends  from  the  soft  palate  to  the 
level  of  hyoid  bone.  It  opens  into  the  oral  cavity, 
through  the  fauces,  bounded  on  either  side  by  the 
anterior  and  posterior  pillars,  between  which  are  the 
tonsils. 

The  laryngeal  part  is  continuous  with  the  oral 
portion  above,  and  below  at  the  level  of  the  cricoid 
cartilage  is  continuous  with  the  esophagus.  Anteriorly, 
it  presents  the  aperture  of  the  larynx,  bounded  in 
front  by  the  epiglottis,  and  laterally  by  the  aryteno- 
epiglottic  folds. 

The  pharynx  is  lined  with  mucous  membrane 
continuous  with  that  lining  the  Eustachian  tube,  the 
nasal  fossae,  the  mouth,  and  the  larynx.  In  the  naso- 
pharynx it  is  covered  by  stratified  ciliated  epithelium; 
in  the  oral  and  laryngeal  portions  it  is  of  the 
stratified  squamous  variety. 


THE   ESOPHAGUS    (GULLET) 

The  esophagus  is  the  tube  connecting  the  pharynx 
with  the  stomach,  and  extends  from  the  level  of  the 
sixth  cervical  vertebra  through  the  diaphragm,  entering 
the  stomach  opposite  the  tenth  or  eleventh  dorsal 


THE  ESOPHAGUS 


261 


vertebra,  a  distance  of  9  or  10  inches,  and  from  the 
incisor  teeth  to  the  beginning  of  the  esophagus  is 
about  6  inches;  thus  making  the  distance  from  the 


Fia.  99 


FIRST  THORA- 
CIC   VERTEBRA 


Twelfth  thora 
cic  vertebra 


Esophagus  and  stomach  in  their  natural  relations  to  the  vertebral 
column  and  the  aorta.     (Testut.) 


262 


THE  ORGANS  OF  DIGESTION 


incisor  teeth  to  the  cardiac  opening  of  the  stomach 
15  to  16  inches.  It  is  the  narrowest  part  of  the  alimen- 
tary canal,  and  presents  two  constrictions,  one  at  its 
commencement,  the  other  at  the  diaphragm. 


Fig.  100 


XCSOPHAGUS 


CARDIAC    ENC 


Stomach  and  duodenum,  the  liver  and  most  of  the  intestines  having  been 
removed.  The  pyloric  end  of  the  stomach  should  be  represented  as  turned 
directly  backward.     (Testut.) 


THE   STOMACH    (GASTER) 

The  stomach  lies  in  the  epigastrium,  left  hypo- 
chondrium,  and  sometimes  the  mesogastrium.  It  is 
the  most  dilated  portion  of  the  alimentary  canal. 
Its  shape  is  pyriform,  the  left  or  larger  portion  is 


THE  STOMACH 


263 


Fig.  101 

eliRl^ACE   OF    MUCOSA 


PARIETAL 
CELL 


called  the  cardia,  and  below  this  is  the  fundus,  the 
right  end  is  termed  the  pylorus.  The  right  opening 
of  the  stomach  is  called  the  pyloric  orifice,  and  the 
left  the  esophageal  orifice,  the  former  opens  into  the 
duodenum,  and  the  latter,  the 
esophagus.  It  is  10  to  12  inches 
in  length,  4  to  5  inches  in  the 
vertical  direction,  and  weighs  4 
to  5  ounces.  Its  capacity  is 
from  3  to  6  pints. 

The  cardiac  orifice  is  the 
highest  part  of  the  stomach,  and 
lies  behind  the  seventh  costal 
cartilage,  1  inch  to  the  left  of 
the  sternum.  The  pyloric  orifice 
lies  about  2  inches  to  the  right 
of  the  midline,  on  a  level  with 
the  upper  border  of  the  first 
lumbar  vertebra;  it  is  guarded 
by  a  valve,  the  pylorus.  Be- 
tween the  two  orifices  the 
stomach  is  sickle-shaped  and 
presents  an  upper  concave  bor- 
der, the  lesser  curvature,  and 
a  lower  convex  border,  the 
greater  curvature.  The  pyloric 
orifice  is  anterior  and  inferior 
to  the  fundus  and  is  in  relation 
with  the  quadrate  lobe  of  the 
liver  and  belly  wall.  The 
stomach  presents  two  surfaces, 
an  anterosuperlor  and  postero- 
inferior. 

The  stomach  has  a  serous  (peritoneal)  coat,  a 
muscular  coat  comprising  a  longitudinal,  circular,  and 
oblique  layer,  an  areolar  coat  of  loose  tissue  (submucous 
coat),  and  a  mucous  coat,  lined  with  columnar  epithe- 
lium. The  latter  is  thickest  near  the  pylorus,  thinnest  at 


(CENTRAL 
CELLS 


Cardiac  gland  \j\  longitudinal 
section.     (F.  H.  G.) 


264 


THE  ORGANS  OF  DIGESTION 


the  fundus,  and  presents,  in  the  empty  condition  of 
the  organ,  numerous  ridges  or  rugce,  which  run  longi- 


FiG.  102 


The  regions  of  the  abdomen  and  their  contents.     Edges  of  costal  cartilage 
in  dotted  outline.     (Gray.) 


tudinally  along  the  great  curvature.  Studded  over  its 
surface  are  many  small  polygonally  shaped  depres- 
sions which  are  the  enlarged  mouths  of  the  gastric 


THE  SMALL  INTESTINE  265 

tubular  glands.  These  are  of  two  kinds,  called  pyloric 
and  cardiac  glands — they  secrete  the  gastric  juice; 
some  are  simply  tubular,  while  others  have  several 
branches  opening  into  a  common  duct.  The  pyloric 
glands  are  most  numerous  at  the  smaller  end,  but  the 
cardiac  glands  (see  Fig.  101,  page  263)  are  found  all 
over  the  stomach,  the  ducts  of  the  latter  being  shorter. 
In  the  cardiac  glands,  between  the  basement  membrane 
and  the  lining  epithelium,  are  numerous  peptic  or 
parietal  cells,  the  others  being  known  as  the  central 
or  chief  cells.  •  Between  the  glands  the  mucous  mem- 
brane contains  lymphoid  tissue,  collected  here  and 
there  into  little  masses  resembling  the  solitary  intes- 
tinal glands,  and  called  the  lenticular  glands.  Beneath 
the  membrane  is  a  muscularis  mucosae.  (See  Fig.  82, 
page  202,  for  blood-supply  of  the  stomach.) 


THE  SMALL  INTESTINE 

The  Duodenum. — The  duodenum  is  about  10  inches 
long,  and  runs  in  a  curved  direction  from  the  pylorus 
of  the  stomach  to  the  jejunum,  which  it  joins  on  the 
left  side  of  the  second  lumbar  vertebra.  The  concavity 
of  the  curve  looks  toward  the  left  and  embraces  the 
head  of  the  pancreas.  It  is  divided,  for  description, 
into  four  parts  or  portions. 

The  Jejunum  and  Ileum. — The  jejunum  includes 
the  first  two-fifths  of  the  remaining  part  of  the  small 
intestine,  running  from  the  left  side  of  the  first  or 
second  lumbar  vertebra  to  the  beginning  of  the  ileum. 
Its  coats  are  thicker  and  more  vascular,  and  are  of  a 
deeper  color  and  larger  caliber  than  the  ileum. 

The  remainder  of  the  small  intestine  is  the  ileum, 
which  ends  by  opening  into  the  inner  side  of  the  com- 
mencement of  the  large  gut  in  the  right  iliac  fossa. 

The  Structure  of  the  Small  Intestines. — The  wall 
of  the  small  intestine,  including  the  duodenum,  con- 


266  THE  ORGANS  OF  DIGESTION 

sists  of  a  serous,  a  muscular,  a  submucous,  and  a 
mucous  coat. 

The  Serous  Coat. — ^This  is  derived  from  the  peri- 
toneum and  surrounds  the  bowel  completely,  except 
in  the  duodenum,  where  only  the  first  portion  is  com- 
pletely covered.  Along  its  mesenteric  border,  where 
the  mesentery  (a  fold  of  peritoneum)  is  attached,  is 
an  uncovered  interval  for  the  entrance  and  exit  of 
arteries,  veins,  nerves,  and  lymphatics  which  pass 
between  the  layers  of  mesentery. 

The  Muscular  Coat. — This  consists  of  an  outer 
longitudinal  and  an  inner  circular  set  of  muscle 
fibers.  These  muscular  layers  propel  the  food  along 
the  intestines,  as  well  as  assist  by  their  action  in  mixing 
it  with  the  intestinal  juices  during  active  digestion. 

The  Submucous  Coat. — This  is  composed  of  areolar 
tissue  and  holds  the  mucous  and  muscular  coats 
together.  It  contains  the  branches  of  the  nutrient 
arteries  to  the  bowel,  previous  to  their  distribution  to 
the  mucous  coat,  also  the  lymph  channels  and  nerves. 
The  lymph  nodules  are  lodged  in  this  layer;  they  are 
pear-shaped  with  their  apex  lying  in  the  mucous 
membrane.  These  are  called  solitary  follicles  and 
Peyer's  patches.  The  submucous  coat  in  the  small 
intestines  extends  up  into  the  valvulse  conniventes. 
In  the  duodenum  the  duodenal  glands  are  lodged  in 
the  submucous  coat. 

The  Mucous  Membrane. — This  is  lined  with  columnar 
epithelium.  It  is  soft  and  velvety  in  appearance. 
The  membrane  is  highly  vascular  near  the  beginning 
of  the  duodenum,  and  gradually  becomes  paler  as  the 
lower  portion  of  the  bowel  is  reached.  The  membrane 
is  thrown  into  folds  called  valvulse  comiiventes.  Each 
fold  is  simply  two  layers  of  membrane  folded  upon 
itself  and  held  together  by  fibrous  tissue.  They 
increase  the  absorbing  surface  of  the  intestinal  canal 
and  retard  the  progress  of  the  food,  according  to  some 
authors.    They  measure  J  to  J  an  inch  in  width,  and 


THE  SMALL  INTESTINE 


267 


extend  to  about  one-half  to  two-thirds  of  the  circum- 
ference of  the  bowel.  The  villi  in  the  mucous  mem- 
brane are  described  under  absorption  (see  page  287). 

The  Intestinal  Glands  or  Glands  of  Lieberkiihn. — These 
are  found  in  the  mucous  membrane  throughout  the 
small  intestines.  They  are  minute  tubular  depressions 
seen  at  the  base  of  the  villi  and  communicate  with 
the  surface  of  the  mucous 
membrane,  upon  which  they 
pour  out  a  special  secretion 
from  the  columnar  cells  which 
line  them;  the  latter  rest  on 
a  thin  basement  membrane, 
which  is  surrounded  by  capil- 
lary vessels. 

The  Duodenal  or  Brunner's 
Glands. — They  are  found  only 
in  the  duodenum.  They  are 
small,  branched,  tubular  glands 
situated  in  the  submucouscoat 
and  open  upon  the  mucous 
membrane  of  the  duodenum 
by  very  small  ducts. 

The  Lymph  Nodules. — ^They 
are  divided  into  solitary  fol- 
licles and  Peyer's  patches. 
Their  bodies  are  in  the  sub- 
mucous coat  and  their  apices 
in  the  mucous  membrane. 

The  solitary  follicles  are 
found  throughout  the  mucous 

and  submucous  layers  of  the  small  and  large  intes- 
tines. They  are  small,  round,  whitish  collections  of 
areolar  tissue  rich  in  leukocytes  or  white  corpuscles, 
and  blood  capillaries,  and  communicate  through  their 
base  with  the  lacteals  of  the  villi.  Each  consists  of 
a  lighter,  central  area,  the  germinal  centre,  where  the 
leukocytes  are  reproducing,  and  an  outer  darker  zone, 


Intestinal  gland  in  longitudinal 
section.    (Testut.) 


268 


THE  ORGANS  OF  DIGESTION 


where  the  cells  are  more  numerous  and  closely  packed 

(Gray). 


Fig.  104 


Duodenal  gland.  _  (Frey.) 
Fig.  105 


Aggregated  lymph  nodule  (Peyer's  patch).     (Testut.) 

Peyer's  patches  are  regarded  as  collections  of  solitary 
follicles,  seen   as   oval   or   rounded   patches,    placed 


THE  LARGE  INTESTINE  269 

lengthwise  with  the  bowel,  measuring  from  i  to  4 
inches  in  length.  Usually  ten  to  sixty  are  present. 
They  are  found  mostly  in  the  ileum.  Peyer's  patches 
are  highly  inflamed  in  typhoid  fever,  and  ulcerate, 
giving  rise  to  hemorrhage  and  perforation  of  the  bowel 
in  severe  attacks  of  the  disease.  (See  Fig.  83,  page 
204,  for  blood-supply  of  the  small  intestines.) 

THE   LARGE   INTESTINE 

The  large  intestine  is  that  part  of  the  alimentary 
canal  which  extends  from  the  end  of  the  ileum  to  the 
anus;  it  is  about  5^  feet  long.  It  commences  by  a 
dilated  part,  the  cecum,  in  the  right  iliac  fossa,  ascends 
to  the  under  surface  of  the  liver,  then  runs  transversely 
across  the  abdomen  to  the  vicinity  of  the  spleen, 
descends  to  the  left  iliac  fossa,  and  forms  the  sigmoid 
flexure,  and  finally  passes  along  back  of  the  pelvis  to 
end  at  the  anus. 

The  Cecum. — ^The  cecum  is  the  large  cul-de-sac 
which  is  the  beginning  of  the  large  intestine,  and  is 
about  3  inches  broad  and  2  j  inches  long.  It  is  variously 
situated,  being  found  upon  and  external  to  the  psoas; 
upon  the  iliacus  muscle  it  lies  internal,  on  the  pelvic 
brim,  or  entirely  within  the  pelvis.  In  any  of  these 
positions  it  is  entirely  surrounded  by  peritoneum. 

The  vermiform  appendix  comes  off  from  the  inner 
and  back  part  of  the  cecum,  near  its  lower  end,  and 
extends  upward  and  inward  behind  it.  This  is  a 
piece  of  gut  of  the  diameter  of  a  goose-quill,  varying 
from  3  to  6  inches  in  length,  curved  upon  itself,  and 
ending  in  a  blind  extremity.  It  tapers  gradually  to 
its  end,  which  is  blunt,  is  completely  invested  by  the 
peritoneum,  which  forms  for  it  a  mesentery  (meso- 
appendix),  and  at  its  connection  with  the  cecum  is 
guarded  by  an  imperfect  valve  (valve  of  Gerlach) .  This 
is  not  always  constant. 

The  ileocecal  valve  guards  the  opening  of  the  small 


270  THE  ORGANS  OF  DIGESTION 

intestine  into  the  large  gut.  This  junction  is  oblique 
and  situated  about  2 J  inches  above  the  lower  extremity 
of  the  cecum.  It  is  a  double  fold  lying  transversely 
to  the  long  axis  of  the  colon.  Each  fold  of  the  valve 
is  made  up  of  the  mucous  and  submucous  coats, 
reinforced  by  some  circular  fibers  from  the  muscular 
coat,  of  each  portion  of  the  gut,  and  is  covered  on  the 
side  toward  the  ileum  with  villi. 

The  Colon. — The  ascending  colon  runs  from  the 
cecum,  above  the  ileocecal  valve,  upward  to  the  under 
surface  of  the  liver  on  the  right  side  of  the  gall-bladder, 
and  then  turns  forward  and  to  the  left  to  form  the 
hepatic  flexure.  The  peritoneum  rarely  forms  for  it 
a  mesocolon;  generally  it  covers  only  the  front  part 
and  the  sides.  It  occupies  the  right  lumbar  and 
hypochondriac  regions. 

The  transverse  colon  arches  across  the  abdomen,  the 
convexity  looking  toward  the  belly  wall,  and  makes 
a  sudden  turn  backward  and  downward  beneath  the 
spleen,  forming  the  splenic  flexure,  and  is  completely 
invested  by  the  peritoneum,  which  holds  it  to  the 
anterior  aspect  of  the  pancreas  and  second  portion 
of  the  duodenum;  by  two  layers  of  peritoneum  called 
the  transverse  mesocolon,  the  upper  surface  of  which 
fuses  with  the  posterior  layer  of  the  great  omentum. 
It  occupies  the  right  hypochondriac,  upper  part  of 
umbilical,  and  left  hypochondriac  regions.  At  the 
splenic  flexure  is  attached  the  phrenocolic  ligament,  a 
fold  of  peritoneum  extending  to  the  diaphragm 
opposite  the  tenth  or  eleventh  rib. 

The  descending  colon  descends  from  the  splenic 
flexure,  to  end  at  the  left  iliac  fossa  in  the  sigmoid 
flexure.  It  is  covered  in  front  and  laterally  by  the 
peritoneum.  It  occupies  the  left  hypochondriac  and 
lumbar  regions. 

The  sigmoid  flexure  ends  in  the  rectum.  From  the 
end  of  the  descending  colon  it  forms  an  S-shaped 
curve,  ending  opposite  the  left  sacro-iliac  joint.     In 


THE  LARGE  INTESTINE 


271 


Fig.   106 


The  stomach  and  intestines,  front  view,  the  great  omentum  having  been 
removed,  and  the  liver  turned  up  and  to  the  right.  The  dotted  line  shows 
the  normal  position  of  the  anterior  border  of  the  liver.  The  dart  points  to 
the  foramen  of  Winslow.     (Testut.) 


272  THE  ORGANS  OF  DIGESTION 

front  of  it  are  the  belly  wall  and  some  coilsof  small 
intestine.  The  peritoneum  forms  a  loose  mesocolon 
for  it.    It  is  the  narrowest  part  of  the  colon. 

The  Rectum. — This  is  the  lowest  part  of  the  large 
intestine,  and  extends  from  the  sigmoid  flexure  to  the 
anus.  It  has  been  divided  into  three  parts:  the  first 
part  extends  from  the  left  sacro-iliac  joint  to  the 
centre  of  the  third  piece  of  the  sacrum;  the  second 
part,  to  the  tip  of  the  coccyx;  and  the  third  part,  to 
the  anus. 

The  rectum  is  about  8  inches  long  and  somewhat 
cylindrical  in  form,  narrower  above  than  the  sigmoid 
flexure,  but  it  enlarges  as  it  descends,  and  just  above 
the  anus  is  remarkably  dilated,  forming  the  ampulla. 
The  first  part  has  a  mesorectum;  the  second  part  is 
covered  by  peritoneum  in  front  and  laterally;  the  third 
part  has  no  peritoneal  covering. 

The  cul-de-sac  of  Douglas  (rectovaginal  pouch)  is  the 
space  in  front  of  the  rectum  and  behind  the  cervix 
of  the  uterus  and  upper  fourth  of  the  vagina.  It  is 
formed  by  the  peritoneum  reflected  over  the  rectum 
to  the  vagina  and  uterus.  In  the  male  it  is  the  space 
formed  between  the  rectum  and  bladder,  and  is  called 
the  rectovesical  space  or  pouch. 

The  Structure  of  the  Large  Intestine. — The  large 
intestine  has  three  coats  comprising  its  wall:  A  serous, 
muscular,  and  mucous.  Its  mucous  membrane  does 
not  possess  the  valvulse  conniventes  nor  villi;  it  is  lined 
by  columnar  epithelium,  and  contains  a  large  number 
of  tubules  lined  by  columnar  epithelium;  they  resemble 
the  glands  of  Lieberkiihn,  and  secrete  a  viscid  fluid, 
rich  in  mucin.  (See  Fig.  83,  page  204,  for  blood- 
supply  of  the  large  intestines.) 


QUESTIONS  273 


QUESTIONS 

1.  What  is  the  length  of  the  alimentary  canal? 

2.  What  organs  constitute  the  alimentary  canal? 

3.  How  many  temporary  teeth  are  there  in  the  child?     Perma- 
nent teeth  in  the  adult? 

4.  Name  the  parts  which  form  a  tooth. 

5.  How  are  the  temporary  teeth  divided  as  to  name  and  number? 
The  permanent  teeth? 

6.  Give  the  position  in  the  alveolar  processes  of  the  incisor 
teeth.    The  canines.    The  bicuspids.    The  molars. 

7.  Give  the  period  of  eruption  of  the  temporary  teeth.     The 
permanent  teeth. 

8.  What  are  the  functions  of  the  tongue? 

9.  What  do  you  understand  by  the  hard  palate?  The  soft 
jpalate? 

10.  What  is  the  isthmus  of  the  fauces? 

11.  Give  the  location  of  the  tonsils. 

12.  Name  the  salivary  glands. 

13.  Which  salivary  gland  is  the  largest?    Give  the  weight  of  each. 

14.  When  do  the  salivary  glands  pour  out  their  secretions?  And 
through  what  structure? 

15.  What  structures  does  the  pharynx  communicate  with? 

16.  How  long  is  the  pharynx,  and  what  three  parts  is  it  subdivided 
into? 

17.  Which  variety  of  epithelium  lines  the  three  portions  of  the 
pharynx? 

18.  What  organ  connects  the  pharynx  with  the  stomach? 

19.  What  is  the  distance  from  the  incisor  teeth  to  the  cardiac 
opening  in  the  stomach? 

20.  Name  the  portions  of  the  stomach. 

21  What  orifices  are  found  in  the  stomach  and  with  what  organs 
do  they  communicate? 

22.  How  many  borders  and  surfaces  has  the  stomach? 

23.  Give  its  dimensions,  weight,  and  average  capacity. 

24.  Name  the  coats  of  the  stomach  wall. 

25.  How  are  the  fibres  in  the  muscular  coat  arranged? 

26.  Name  the  glands  found  in  the  membrane  of  the  stomach. 

27.  What  structures  secrete  the  gastric  juice? 

28.  Where  are  the  pyloric  glands  in  the  stomach  located?  The 
cardiac  glands? 

29.  Do  the  cardiac  and  pyloric  glands  communicate  with  the 
internal  surface  of  the  stomach?  Through  what  structure  is  their 
secretion  poured  out? 

30.  Name  the  cells  formed  in  a  cardiac  gland. 

31.  How  long  is  the  duodenum? 

32.  What  portions  of  the  alimentary  canal  does  the  duodenum 
connect  and  communicate  with? 

33.  What  are  the  divisions  of  the  small  intestine  called? 

34.  Name  the  coats  forming  the  structure  of  the  small  intestine. 

35.  Which  variety  of  the  epithelium  lines  the  small  intestine? 

18 


274  THE  ORGANS  OF  DIGESTION 

36.  What  arc  the  valvulsB  conniventes?    What  is  their  function? 

37.  Where    are   the   glands   of   Lieberkiihn   found?      Glands    of 
Brunner? 

38.  Do  the  above  glands  communicate  with  the  surface  of  the 
mucous  membrane  of  the  intestines? 

39.  Where  are  solitary  lymph  follicles  found?    Peyer's  patches? 

40.  Describe  a  Peyer's  patch. 

41.  How  long  is  the  large  intestine? 

42.  What  is  the  length  of  the  appendix? 

43.  Name  the  portions  of  the  colon. 

44.  How  long  is  the  rectum? 

45.  What  is  its  lower  opening  called? 

46.  Name  the  coats  of  the  large  intestine. 

47.  What  type  of  epithelium  is  present  in  the  large  intestine? 

48.  Are  valvulae  connivents  found  in  the  large  intestine? 

49.  Does  the  mucous  membrane  of  the  colon  contain  glands? 

50.  What  variety  of  secretion  do  the  glands  of  the  colon  secrete? 


CHAPTER  XII 
DIGESTION 

The  digestive  apparatus  consists  of  the  entire 
alimentary  canal,  including  the  mouth,  pharynx, 
esophagus,  stomach,  small  intestines — duodenum, 
jejunum,  ileum;  large  intestines — cecum,  colon,  rec- 
tum; and  the  accessory  organs,  as  the  teeth,  salivary 
glands,  tongue,  gastric  and  intestinal  glands,  the 
pancreas,  and  liver. 

Mastication  and  Insalivation. — Mastication. — This  is 
the  process  whereby  the  food  is  chewed  or  undergoes 
a  mechanic  disintegration,  which  permits  of  it  being 
properly  acted  upon  by  the  saliva  and  formed  in  such 
condition  to  be  swallowed;  this  is  brought  about  by 
the  action  of  the  teeth,  tongue,  and  muscles  of  masti- 
cation, which  act  upon  the  lower  jaw,  bringing  it 
with  the  contained  teeth  against  the  upper  teeth  in 
the  maxilla. 

Insalivation. — This  is  the  mixing  of  the  food  with 
the  saliva  during  the  act  of  mastication.  The  saliva 
is  constantly  bathing  the  mucous  membranes  of  the 
oral  cavity  and  its  contents;  however,  during  mastica- 
tion there  is  a  marked  increase  of  this  complex  fluid 
secreted  from  the  salivary  glands^parotid,  sub- 
maxillary and  sublingual,  and  palatine  glands  in  the 
roof  of  the  mouth. 

The  Saliva. — ^This  is  a  complex  chemic  fluid  com- 
posed of  the  mixed  secretions  of  all  the  salivary  glands. 
It  is  a  frothy,  slightly  turbid,  viscid  fluid.  Its  reac- 
tion under  normal  conditions  is  alkaline.  It  may  be 
neutral  or  acid  in  some  individuals,  in  which  fermen- 


276  DIGESTION 

tation  is  going  on  from  decayed  teeth  or  particles  of 
food  lying  in  the  recesses  of  the  teeth  and  mouth,  or 
disorders  of  digestion.  Under  the  microscope,  the 
saliva  will  show  epithelial  cells,  salivary  corpuscles 
resembling  white  corpuscles,  particles  of  food,  and 
various  microorganisms  (germs). 

The  Physiologic  Actions  of  Saliva. — The  constant 
presence  of  saliva  in  the  mouth  is  essential  to  the 
process  of  digestion.  It  has  a  double  duty  to  perform, 
called  physical  and  chemical. 

Physically  the  mucin  present  in  the  saliva  forms 
the  particles  of  food  into  a  consistent  mass  after  the 
food  has  been  softened  and  moistened  while  mastica- 
tion has  been  going  on,  and  renders  it  in  such  shape 
to  be  swallowed  (deglutition). 

The  Chemical  Action  of  Saliva. — Its  main  property 
is  the  changing  or  converting  of  starch  into  sugar 
by  the  means  of  a  starch-changing  ferment  or  enzyme, 
which  is  supposed  to  belong  to  the  group  of  proteins, 
called  ptyalin,  in  the  saliva. 

Deglutition  (the  act  of  swallowing). — This  is  a  com- 
plicated function  due  to  the  action  of  the  muscles  of 
the  tongue,  soft  palate,  pharynx,  and  esophagus  acting 
upon  the  food,  called  a  bolus  after  it  has  been  chewed 
or  masticated  by  the  teeth,  whereupon  these  structures 
force  it  from  the  mouth  into  the  pharynx  and  thence 
through  the  esophagus  into  the  stomach. 

At  the  beginning  of  deglutition  the  mouth  is  closed 
and  the  tip  of  the  tongue  is  rested  against  the  incisor 
teeth.  There  is  a  temporary  suspension  of  respiration. 
The  tongue  arches  from  before  backward  against  the 
roof  of  the  mouth,  due  to  the  action  of  the  intrinsic 
muscles,  those  contained  therein,  and  forces  the 
bolus  of  food  through  the  opening  leading  from  the 
mouth  to  the  pharynx.  These  actions  are  under 
the  control  of  the  will.  The  food  upon  reaching  the 
pharynx  is  seized  by  the  constrictor  muscle  of  this 
organ  and  by  a  sphincter  action  is  forced  through  the 


GASTRIC  DIGESTION  277 

esopahgus,  which  continues  this  muscular  wave 
(peristaltic  wave).  Some  physiologists  say  that  the 
food  passes  through  the  pharynx  and  esophagus  due 
to  a  rise  in  pressure.  Food  as  it  passes  into  the 
pharynx  would  enter  the  nasal  cavities  and  larynx, 
but  the  former  cavities  are  closed  by  the  action  of 
the  tensor  palate  and  levator  palati  muscles  which 
contract  and  draw  upward  and  backward  the  palate 
until  it  meets  the  posterior  wall  of  the  pharynx.  The 
larynx  is  closed  from  the  food,  for  just  at  the  time  of 
or  before  deglutition  there  is  a  temporary  suspension 
of  inspiration,  and  the  larynx  is  drawn  up  under  the 
base  of  the  tongue  and  the  opening  to  it  closed  by 
the  epiglottis  falling  downward  and  backward,  pre- 
venting food  from  entering  the  larynx. 

Gastric  Digestion. — The  digestion  of  the  food  on 
reaching  the  stomach  is  a  further  step  in  its  gradual 
preparation  into  a  more  liquid  or  semiliquid  form  to 
enable  the  capillaries  and  lymph  vessels  within  the 
villi  of  the  small  intestines  to  absorb  it  after  being 
acted  upon  by  the  intestinal  and  pancreatic  juices  in 
the  small  intestines. 

The  walls  of  the  mucous  membrane  of  the  stomach 
between  the  periods  of  active  digestion  are  being 
bathed  with  an  alkaline  secretion  derived  from  the 
glands  in  its  wall.  This  secretion  of  the  gastric  juice 
has  been  produced  reflexly  by  psychic  influences,  such 
as  the  sight  of  food,  and  is  also  due  to  an  irritation 
of  the  mucous  membrane  produced  by  the  presence 
of  food  in  the  stomach.  After  digestion  has  com- 
menced ■  this  secretion  is  profuse.  The  bloodvessels 
of  the  mucous  membrane  become  congested  and  the 
glands  show  activity.  The  perpetual  secretion  of 
gastric  juice  is  supposed  to  be  due  to  some  chemic 
change  taking  place,  the  resultant  substance  acting 
as  a  specific  stimulant  to  the  cells  of  the  glands. 

When  food  passes  through  the  cardiac  orifice  due 
to  the  peristaltic  waves  and  pressure  within  the  esoph- 


278  DIGESTION 

agus  during  deglutition  or  swallowing.  The  stomach 
receives  the  food,  whereupon  the  muscular  fibers 
of  the  cardiac  and  pyloric  orifices  close  by  a  sphincter- 
like contraction.  The  food  is  held  within  the  stomach 
for  a  few  moments,  then  is  turned  over  and  over  and 
moulded  by  the  muscular  contractions  of  the  stomach 
until  it  is  reduced  to  a  liquid  or  semiliquid  consist- 
ency called  chyme,  by  the  action  of  the  gastric  juice. 
The  pyloric  portion  of  the  stomach  becomes  shaped 
like  a  tube,  and  the  fundus  or  most  dilated  portion  of 
the  stomach  contracts  and  forces  the  food  (chyme) 
into  the  duodenum,  where  it  is  conveyed  by  a  similar 
peristaltic  contraction  of  its  walls  into  the  small 
intestine.  There  is  no  given  time  for  emptying  the 
stomach.  As  the  food  is  liquefied  it  is  forced  out  of 
the  stomach  and  then  the  semisolid  particles  of  the 
diet  which  are  not  digested  by  gastric  juice  are  passed 
from  the  stomach,  leaving  it  empty  except  for  the 
alkaline  secretion  which  is  mucous,  and  protects  its 
walls.  Digestion  in  the  stomach  lasts  from  two  to 
five  hours,  depending  upon  the  food,  quantity  and 
quality,  pathologic  conditions,  etc.  No  nourishment 
is  absorbed  by  the  lymph  or  bloodvessels  of  the 
stomach. 

Gastric  Juice. — Under  normal  physiologic  conditions 
gastric  juice  is  a  thin,  almost  colorless  liquid,  with  a 
characteristic  odor  and  acid  reaction.  The  average 
of  acidity  varies;  normally  it  is  0.02  per  cent.  The 
acidity  is  due  to  the  presence  of  hydrochloric  acid, 
and  in  certain  conditions  of  health  and  disease,  lactic 
acid  may  be  found.  As  a  result  of  disease,  the  acidity 
may  be  increased,  decreased,  or  entirely  absent.  The 
gastric  juice  contains  in  addition  to  the  above,  pepsin 
and  rennin,  two  proteolytic  ferments  or  enzymes;  the 
former  is  active  only  in  an  acid  medium,  and  the 
latter  is  the  ferment  which  curdles  milk  or  divides 
it  into  a  solid  portion,  casein,  and  the  liquid  portion, 
whey.   The  chemic  nature  of  these  enzymes  is  unknown. 


INTESTINAL  DIGESTION  279 

Gastric  juice  also  contains,  in  addition,  large  amounts 
of  water,  ammonium,  calcium,  potassium,  and  sodium 
chlorides;  calcium,  magnesium,  and  ferric  phosphate 
are  present  in  small  amounts. 

Pepsin  converts  proteins  into  peptones.  The  process 
is  most  complicated  and,  as  described  by  Kiihne  in 
his  investigations,  is  as  follows:  The  protein  material 
is  changed  first  into  acid-albumin.  If  the  solution  is 
rendered  alkaline,  acid  albumin  will  be  precipitated. 
Then  the  acid  albumin  is  split  up  into  several  soluble 
proteins  called,  collectively,  primary  proteoses:  albu- 
mose  from  albumin,  globulose  from  globulin,  etc.  The 
latter  in  turn  take  more  water  and  split  up  into 
another  group  of  proteins  called  secondary  proteoses  or 
deuteroproteoses.  The  latter  undergo  further  change 
and  form  peptones. 

Rennin  curdles  cows'  milk  very  rapidly  at  the  body 
temperature.  The  casein  in  the  milk  is  changed  from 
a  soluble  protein  into  a  solid  clot  which  finally  becomes 
firm  and  squeezes  the  whey  out  of  the  mass.  The  curd 
of  cows'  milk  is  a  solid  clot,  whereas  the  curd  of  human 
milk  is  formed  into  very  fine  particles,  thus  rendering 
it  more  digestible  to  the  infants. 

Intestinal  Digestion. — Upon  reaching  the  small  in- 
testine the  chyme  containing  the  partially  digested 
fats,  meats,  sugars,  the  peptones,  etc.,  is  acted  upon 
by  the  pancreatic  and  intestinal  juices,  and  bile, 
all  at  the  same  time;  the  action  of  each  of  these 
juices  will  be  considered  individually.  As  these 
partially  digested  particles  are  acid  in  reaction,  as 
they  pass  through  the  intestines  they  cause  a  reflex 
stimulation  of  its  cells  w^hich  pour  out  an  alkaline 
secretion. 

The  Pancreatic  Juice. — This  is  secreted  by  the  cells 
of  the  glands  of  the  pancreas  and  reaches  the  duodenum 
by  way  of  the  pancreatic  duct  (Wirsung),  which  opens 
into  the  small  intestines,  together  with  or  ahead  of 
the  bile  from  the  liver,  and  is  supposed  to  be  mixed 


280  DIGESTION 

with  the  bile  and  food  material  at  the  same  time. 
It  is  alkaline  in  reaction,  and  contains  three  active 
enzymes — trypsin,  amylopsin,  and  steapsin. 

Trypsin  is  a  more  active  ferment  than  pepsin,  and 
continues  the  digestion  of  peptones  into  a  more  soluble 
form  than  pepsin.  It  acts  best  in  an  alkaline  medium. 
The  function  of  this  ferment  is  to  convert  proteins 
into  peptones,  as  pepsin  does  in  the  gastric  digestion. 

Amylopsin  is  the  ferment  in  the  pancreatic  juice 
which  converts  the  undigested  particles  of  starch 
in  the  food  into  sugar — maltose.  It  acts  similarly  to 
the  ferment  ptyalin  in  the  saliva.  As  starch  digestion 
ceases  with  the  entrance  of  food  into  the  stomach,  the 
action  of  the  amylopsin  ferment  in  the  pancreatic 
juice  is  important,  in  order  that  the  starches  are 
completely  digested,  for  they  belong  to  the  carbo- 
hydrates which  are  essential  as  a  food,  to  be  used  by 
the  tissues  in  the  production  of  heat  and  energy. 

Steapsin  is  the  ferment  or  enzyme  which  splits  the 
fats  remaining  in  the  partially  digested  food  into 
fatty  acids  and  glycerin.  The  fatty  acids  coming 
in  contact  with  alkaline  salts  in  the  intestine  are 
saponified  and  form  a  soap,  the  products  are  absorbed 
and  combine  again  to  form  a  neutral  fat,  which  is 
used  by  the  tissues  after  absorption.  This  recombina- 
tion may  occur  in  the  epithelial  cells  of  the  intestines. 
Some  of  the  fat  is  emulsified  during  the  formation 
of  the  soap,  appearing  as  a  creamy  emulsion,  before 
being  absorbed. 

Intestinal  Juice. — We  have  described  or  endeavored 
to  make  clear  how  the  food  we  eat  has  been  gradually 
reduced  to  a  state  in  w^hich  it  can  be  absorbed — liquid 
or  semiliquid.  There  still  remains,  as  has  been  proved 
in  animals  and  human  beings,  chyme  in  the  intestines, 
containing  sugars,  apparently  non-absorbable  without 
undergoing  further  change.  This  is  produced  by  the 
action  of  the  intestinal  juice  and  the  contained  enzyme 
or  ferment  invertin.    The  latter  converts  these  sugars — 


INTESTINAL  DIGESTION  281 

saccharose,  maltose,  and  lactose — into  dextrose  and 
levulose,  two  varieties  of  sugar  which  are  assimilable. 
These  two  sugars  together  form  what  is  called  invertin 
sugar. 

The  Part  Played  by  the  Bile  in  Digestion. — ^The  liver 
plays  a  large  part  in  digestion  and  nutrition  of  the 
body.  This  important  relation  is  due  chiefly  to  the 
secretion  from  the  liver  cells  termed  bile. 

Bile  is  continually  secreted  from  the  cells  within 
the  lobules  of  the  liver,  and  is  collected  by  the  tiny 
biliary  capillaries  which  join  larger  vessels  to  finally 
end  in  the  right  and  left  hepatic  ducts  which  leave 
the  transverse  fissure  of  the  liver,  passing  downward 
after  receiving  the  cystic  duct  from  the  gall-bladder, 
and  then  pass  downward  and  inward  as  the  common 
bile  duct  to  open  into  the  duodenum.  The  bile  is 
stored  in  the  gall-bladder  until  needed,  when  it  passes 
through  the  above-mentioned  passages  to  aid  in  the 
intestinal  digestion  of  the  food. 

Bile  obtained  from  the  gall-bladder  is  of  a  thick, 
viscid  character,  green  or  golden  yellow  in  color, 
specific  gravity  of  1.010  or  1.020.  It  is  composed 
chiefly  of  water,  small  quantities  of  sodium  glycocho- 
late,  and  sodium  taurococholate,  cholesterin,  free  fat, 
sodium  palmitate  and  stearate,  lecithin,  other  organic 
matters;  sodium  and  potassium  chlorides,  sodium  and 
calcium  phosphates,  sodium  carbonate. 

The  flow  of  bile  from  the  liver  is  continuous,  influ- 
enced by  the  process  of  digestion.  It  increases  as 
soon  as  food  reaches  the  stomach,  but  its  greatest 
flow  is  not  noted  until  about  two  hours  later.  After 
this  it  decreases  by  degrees,  but  never  entirely  stops. 
The  bile  is  forced  out  of  the  gall-bladder  by  a  con- 
traction of  its  muscular  walls. 

The  Physiologic  Functions  of  the  Bile. — (1)  Aids  in 
digestion  of  fats,  and  by  its  contained  bile  salts 
increases  the  action  of  the  pancreatic  enzymes  in 
splitting  neutral  fats,  digesting  starches  and  peptones; 


282  DIGESTION 

(2)  arrests  gastric  digestion,  by  neutralizing  and  pre- 
cipitating the  proteins  which  have  not  been  entirely 
digested;  and  by  preparing  the  way  for  intestinal 
digestion;  (3)  a  slight  antiseptic  action.  It  is  a  known 
fact,  that  if  bile  is  not  secreted  in  the  human  being, 
putrefactive  changes  take  place,  with  the  resultant 
formation  of  foul  gases,  and  other  products  noted  in 
the  feces;  (4)  increases  peristalsis,  which  aids  in  the 
proper  contractile  movements  of  the  walls  of  the  intes- 
tines, favoring  intestinal  digestion  and  defecation. 

The  Functions  of  the  Large  Intestine. — The  large 
intestine  is  that  portion  of  the  bowels  which  commences 
at  the  ileum  and  terminates  at  the  anus.  Its  sub- 
divisions are  termed:  the  cecum,  ascending,  trans- 
verse, descending,  and  sigmoid  colon,  and  the  rectum. 
It  is  a  large  musculomembranous  tube  covered  exter- 
nally by  the  peritoneum,  and  is  from  4|  to  5  feet  in 
length  in  a  normal  adult. 

The  contents  of  the  colon  consist  of  the  undigested 
products  of  digestion,  as  a  result  of  the  food  being 
acted  upon  by  the  saliva,  gastric,  pancreatic,  and 
intestinal  juices,  and  the  bile;  the  nutritive  parts, 
peptones,  fatty  acids,  glycerin,  etc.,  being  absorbed; 
the  resulting  liquid  and  waste  material  contains 
undigested  particles  of  cereals,  vegetables,  seeds, 
cellulose,  etc.,  which  are  passed  into  the  rectum  by  a 
peristaltic  wave  of  its  walls  similar  to  the  phenomena 
taking  place  in  the  small  intestines,  then  expelled 
from  the  rectum  during  the  act  of  defecation. 

The  mucus  secreted  by  the  glands  of  the  large 
bowel  incorporates  the  liquid  material  and  passes  it 
toward  the  sigmoid  flexure  of  the  colon,  where  it  is 
held  prior  to  the  emptying  of  the  bowel. 

Defecation. — This  is  the  act  whereby  the  waste 
material  resulting  from  digestion  is  expelled  from 
the  intestine  by  the  rectum  and  passes  through  the 
anus.  It  occurs  normally  once  a  day.  The  walls 
of   the   sigmoid   colon   contract   and    force   the   feces 


DIGESTION  IN  INFANTS  283 

into  the  rectum.  This  gives  rise  to  the  sensation 
felt  prior  to  defecation,  then  the  longitudinal  and 
circular  fibers  of  the  rectum  contract,  and  pressing 
downward  on  the  mass,  force  it  through  the  relaxed 
sphincter  ani  muscles.  The  wall,  contraction  of  the 
diaphragm,  the  muscles  of  the  abdomen  levator  ani 
and  coccygeus,  sphincter  ani  muscles  all  aid  in  the 
expulsion  of  the  feces. 

Digestion  in  Infants. — The  Saliva. — This  is  very 
scanty  at  birth,  but  gradually  increases.  At  the 
fourth  month  it  is  of  sufficient  quantity  and  of  such 
strength  as  to  be  capable  of  digestion.  When  the 
teeth  are  erupted  there  is  a  marked  increase  in  saliva, 
and  from  the  eighth  to  tenth  month  it  will  digest  a 
small  amount  of  starch. 

The  Capacity  of  the  Stomach. — It  is  essential  for  the 
nurse  to  acquire  a  knowledge  of  the  capacity  of  the 
infant's  stomach  from  birth  to  the  fourteenth  month. 
The  following  capacities  may  vary  somewhat,  and  the 
nurse's  judgment  must  influence  her  in  certain  cases 
if  called  upon  to  prepare  a  bottle  for  the  baby,  in 
regard  to  the  quantity  of  modified  milk  to  be  used  in 
each  feeding  (according  to  Holt): 

Age.  Average  capacity. 

Birth 1 .  20  ounces 

Two  weeks 1 .  50  ounces 

Four  weeks .  2 .  00  ounces 

Six  weeks 2 .  27  ounces 

Eight  weeks 3 .  37  ounces 

Ten  weeks     .  .  - 4 .  25  ounces 

Twelve  weeks 4 .  50  ounces 

Fourteen  to  eighteen  weeks 5.00  ounces 

Five  to  six  months 5 .  75  ounces 

Seven  to  eight  months 6 .  88  ounces 

Ten  to  eleven  months 8 .  14  ounces 

Twelve  to  fourteen  months 8 .  90  ounces 

Gastric  Digestion. — Breast-fed  babies  retain  the  milk 
in  the  stomach  for  about  an  hour  after  nursing, 
bottle-fed   babies   about   one   hour  and   a  half:   this 


284  DIGESTION 

increases  with  age.  In  the  very  young  the  stomach 
is  simply  a  reservoir  for  the  food,  when  it  is  passed 
into  the  small  intestine.  Pepsin  has  been  found  in 
the  infant's  stomach,  and  some  hydrochloric  acid, 
which  accounts  for  its  acidity.  And  in  early  life  some 
lactic  acid. 

Rennin  plays  an  important  part  in  infant  digestion. 
It  is  the  ferment  which  coagulates  mothers'  and  cows' 
milk,  splitting  the  casein  into  a  solid  mass  (clot), 
and  whey  (the  liquid  portion).  Intestinal  digestion  is 
not  very  active  in  infancy,  the  ferment  from  the 
pancreas  acting  more  like  ptyalin  in  the  saliva  of 
the  adult.  Absorption  of  nourishment  takes  place 
from  the  mucous  membrane  of  the  intestines.  In 
breast-fed  infants  2  to  5  per  cent,  of  the  fat  and 
protein  pass  directly  through  the  intestines;  in  bottle- 
fed  ones,  1  to  3  per  cent,  more  for  the  fats,  and  a 
still  greater  increase  for  the  proteins  (Appelmann). 
Numerous  bacteria  are  present  in  the  intestinal  canal 
of  infants.  They  may  play  some  part  in  digestion; 
however,  it  is  one  on  which  neither  life  nor  health 
depends. 

QUESTIONS 

1.  What  organs  constitute  the  digestive  apparatus? 

2.  Describe  mastication;  insalivation. 

3.  Name  the  glands  which  secrete  saliva. 

4.  Is  the  reaction  of  saliva  acid  or  alkaline? 

5.  Describe  the  physiologic  (physical)  action  of  saliva;  chemical. 

6.  What  change  takes  place  in  the  bloodvessels  of  the  mucous 
membrane  of  the  stomach  during  digestion? 

7.  What  part  do  the  muscular  coats  of  the  stomach  play  during 
digestion? 

8.  How  is  the  food  held  within  the  stomach  while  the  walls 
contract  upon  it? 

9.  What  do  you  understand  by  the  term  chyme? 

10.  How  long  does  digestion  last  in  the  stomach? 

11.  What  juice  is  secreted  from  the  glands  of  the  mucous  mem- 
brane of  the  stomach  during  digestion? 

12.  Do  the  blood  or  lymph  vessels  absorb  any  nourishment  from 
the  stomach? 

13.  Is  gastric  juice  acid  or  alkaline  in  reaction  during  digestion? 


QUESTIONS  285 

14.  What  is  the  acidity  due  to?  What  percentage  of  hydrochloric 
acid  is  normally  present  in  the  gastric  juice? 

15.  What  is  the  function  of  pepsin  in  the  gastric  secretion? 
Rennin? 

16.  Is  the  intestinal  secretion  acid  or  alkaline  in  reaction? 

17.  Name  the  enzymes  found  in  the  pancreatic  juice. 

18.  Give  briefly  the  function  of  the  enzymes  trypsin,  amylopsin, 
steapsin,  as  regards  their  action  during  intestinal  digestion. 

19.  Name  the  enzyme  present  in  the  intestinal  juice  and  give  its 
function. 

20.  What  cells  secrete  the  bile  and  how  does  it  leave  the  liver?' 

21.  Name  the  organ  in  which  bile  is  stored. 

22.  How  does  the  bile  reach  the  intestine  from  the  liver  and 
gall-bladder? 

23.  Give  the  physiologic  functions  of  bile. 

24.  Give  the  contents  of  the  colon  following  intestinal  digestion. 

25.  Give  the  capacity  of  the  infant's  stomach  at  birth;  two,  four, 
six,  eight,  ten,  twelve,  fourteen  to  eighteen  weeks;  five  to  six,  seven 
to  eight,  twelve  to  fourteen  months. 

26.  Describe  the  functions  of  the  stomach  during  gastric  digestion 
in  infants. 

27.  In  which  portion  of  the  alimentary  canal  is  the  nourishment 
absorbed  from  during  infant  digestion? 


CHAPTER  XIII 
ABSORPTION 

Absorption  is  the  process  whereby  the  nutritive 
material,  lymph,  is  transferred  from  the  tissues;  the 
serous  cavities — pericardium,  peritoneum,  etc.;  and 
mucous  membranes  into  the  blood.  The  lymph  is 
absorbed  from  the  mucous  membrane  of  the  alimen- 
tary canal,  as  it  is  the  principal  source  of  nutritive 
material  used  by  the  body  for  the  maintenance  of 
the  quantity  and  quality  of  the  blood;  while  the 
lymph  absorbed  from  the  serous  cavities  and  tissues 
represents  a  reabsorption  of  the  nutritive  materials 
which  have  escaped  through  the  capillary  walls,  and 
are  returned  to  the  veins  through  the  lymphatic 
vessels.  Were  this  lymph  allowed  to  collect  in  the 
tissues,  there  would  occur  an  excessive  accumulation, 
and  this  condition  would  be  readily  accounted  for  in 
the  swelling  of  the  subcutaneous  tissue  and  organs 
giving  rise  to  a  pathologic  condition  termed  edema. 

Under  the  chapter  on  digestion  it  was  shown  how 
the  food  we  eat  is  reduced  to  a  liquid  condition  by 
the  action  of  the  various  gastric,  pancreatic,  and 
intestinal  juices  and  their  ferments.  This  nutritive 
material  is  taken  up  by  the  mucous  membrane  of 
the  intestine  and  absorbed,  then  reaches  the  blood- 
current  by  way  of  the  lymph  channels — lacteals,  and 
finally  reaches  the  thoracic  duct;  or  by  way  of  the 
venous  capillaries  of  the  mesenteric  veins,  and  is  carried 
to  the  liver,  and  thence  to  the  right  side  of  the  heart. 

Before  understanding  the  methods  of  food  absorp- 
tion, a  description  of  the  mucous  membrane  of  the 
intestines  is  necessary. 


THE  FUNCTION  OF  THE  VILLI  287 

Structure  of  the  Villi. — The  mucous  membrane  of 
the  small  intestine  is  covered  by  tiny  conical  processes 
which  extend  from  the  end  of  the  pylorus  of  the  stomach 
to  the  end  of  the  ileum.  These,  when  examined  under 
the  microscope,  show  a  conical  process  covered  with 
columnar  epithelial  cells,  each  cell  containing  a  nucleus, 
and  here  and  there  goblet  cells  which  secrete  mucus. 
The  epithelial  cells  rest  upon  a  basement  membrane. 
In  the  body  of  the  villus  that  portion  within  the 
mucous  membrane  contains  a  net-work  of  connective 
tissue  supporting  arterioles,  capillaries,  venules,  and 
lymphatic  vessels.  In  the  centre  of  the  villus  is  a 
lymph  capillary,  usually  single,  with  epithelial  cells  in 
its  wall. 

The  Function  of  the  Villi. — The  action  of  the  cells 
of  the  villi  during  digestion  is  to  absorb  the  nutritive 
products  of  digestion.  These  products  are  taken 
from  the  intestinal  canal  and  transferred  into  the 
lymph  spaces  within  the  body  of  the  villi,  from  which 
they  are  finally  taken  up  by  the  blood  capillaries  and 
lymphatics.  There  are  two  routes  by  which  the  nutri- 
tive material  passes  into  the  general  blood  stream. 
The  capillaries  which  enter  the  villi  and  are  in  inti- 
mate relation  with  the  lymph  space  give  up  their 
nutritive  materials  (blood  plasma)  by  a  transudation 
through  their  walls,  which  forms  the  lymph;  mean- 
time the  nutritive  material  absorbed  from  the  intes- 
tines by  the  cells  of  the  villi  undergoes  metabolic 
changes  and  enters  the  arterial  capillaries  from  the 
lymph  spaces.  This  fenourished  blood  in  the  arterial 
capillaries  passes  into  the  venules  and  then  into  the 
larger  veins  of  the  intestines,  to  be  conveyed  to  the 
liver,  which  uses  it  to  maintain  its  functions.  The 
lymph  contained  in  the  lymph  spaces  within  the  villi 
is  called  chyle  (a  milk-white  fluid),  which  is  absorbed 
by  the  lymphatic  vessels  called  lacteals,  and  these 
empty  into  the  large  mesenteric  lymphatics  to  drain 


288 


ABSORPTION 


into  the  thoracic  duct,  and  the  latter  communicates 
with  the  left  subclavian  vein,  and  thus  returns  the 
excess  of  lymph  back  to  the  blood-stream. 

The  wonderful  aspect  of  absorption  is  the  apparently 
unsolvable  problem  in  regard  to  how  these  numbers 
of  cells  in  the  villi  of  the  intestinal  mucous  membrane 


Fia.   107 


PLANE    OF    MU-  

COUS    SOHFACC.~~Q 


MUCOUS   COAT 


Mucosa  of  small  intestine  in  ideal  vertical  cross-section.     (Testut,  after 
Heitzmann.) 


can  absorb  the  different  constituents  of  the  nutritive 
materials  from  the  alimentary  canal  and  transfer 
them  into  the  lymph  spaces  to  be  absorbed  by  the 
blood  capillaries  and  lymphatics. 

It  is  supposed  to  be  due  to  a  "selective  action'* 
based  on  their  organization  and  living  condition,  an 
action   which   is   to   a   great   extent   conditioncfl    and 


QUESTIONS  289 

limited  by  the  degree  of  diffusibility  of  the  substances 
to  be  absorbed  (Brubake'r's  Physiology,  p.  225). 


QUESTIONS 

1.  Describe  absorption. 

2.  By  what  two  sources  does  lymph  reach  the  blood  current? 

3.  What  is  the  function  of  the  cells  in  the  villi  of  the  mucous 
membrane  of  the  small  intestines? 

4.  Where  are  the  lymph  spaces  found? 

5.  What  do  you  understand  by  the  term  lacteals? 

6.  What  is  chyle? 

7.  How  does  the  nutritive  material  absorbed  by  the  cells  of 
the  villi  reach  the  arterial  capillaries?  Where  is  this  material 
conveyed? 

8.  Where  is  the  lymph  absorbed  by  the  lacteals  from  the  lymph 
spaces  conveyed? 

9.  Name  the  vessels  found  in  a  villi. 


19 


CHAPTER   XIV 
SECRETION 

Secretion  is  a  term  applied  to  a  process  by  which 
a  portion  of  the  constituents  of  the  blood  are  separ- 
ated from  the  blood-stream,  by  the  activities  of  the 
endothelial  cells  of  the  capillary  walls,  as  the  blood 
flows  through  the  capillaries.  In  this  process  the 
endothelial  cell  is  aided  by  the  physical  forces — 
diffusion,  osmosis,  and  filtration.  The  materials  thus 
separated  are  collectively  termed  lymph  (Brubaker). 

These  secretions  are  utilized  and  adapted  to  many 
and  complex  functions,  dependent  upon  the  secre- 
tory organ  which  secretes  the  fluid  and  the  membrane 
it  is  poured  out  upon.  They  enable  the  tissues  of 
the  body  to  repair,  grow,  and  produce  heat  and 
energy.  Others  are  to  promote  digestion,  etc.,  remove 
foreign  bodies  (dust,  etc.)  from  membranes,  as  the 
conjunctiva,  to  prevent  friction  between  the  serous 
membranes,  as  the  pericardium,  pleura,  and  peri- 
toneum; and  to  prevent  friction  between  the  ex- 
tremities of  the  bones  entering  into  the  formation  of 
the  joints,  as  the  fluid  in  synovial  membranes. 

Secretions  are  divided  into  internal  and  external 
secretions.  Internal  secretions  are  fluids  secreted  by 
the  epithelial  cells  of  certain  organs  of  the  body  which 
do  not  possess  any  ducts  by  which  their  secretion 
is  poured  into  any  cavity  or  organ,  but  is  reabsorbed 
into  the  blood,  and  the  contained  specific  constituents 
aid  in  the  nutrition  of  the  body.  These  organs  are: 
the  thyroid,  thymus,  adrenal,  spleen,  pituitary  glands, 
hypophysis,  etc.  (See  description  of  the  Ductless 
Glands,  page  303.) 


THE  SECRETING  MEMBRANES  291 

External  secretions  are  fluids  of  a  definite  consist- 
ency and  known  function  which,  when  secreted  by 
the  epithelial  cells  and  poured  from  the  organ  by 
means  of  a  duct  or  ducts  on  to  the  membrane  they  are 
to  bathe,  etc.,  perform  this  given  activity.  Such 
secretions  are:  the  saliva,  mucus,  milk,  gastric  juice, 
sebaceous  matter,  etc. 

The  epithelium  lining  the  secretory  organs  have 
a  general  similar  histologic  arrangement,  and  resem- 
blance; however,  the  difference  in  the  constituents  of 
the  secretion  is  supposed  to  be  based  upon  their  ulti- 
mate chemic  structure. 

The  epithelial  secretory  organ  consists  of  a  thin, 
delicate  membrane  lined  on  its  functionating  surface 
by  a  layer  of  epithelial  cells  and  on  the  outer  side 
by  a  net-work  of  capillary  bloodvessels,  lymph  vessels, 
and  nerves. 

The  epithelial  secretor  organs  are  subdivided  into: 
(1)  secreting  membranes;  (2)  secreting  glands. 


THE    SECRETING   MEMBRANES 

These  are  the  membranes  lining  the  pulmonary 
and  gastro-intestinal  tracts,  the  genito-urinary  tracts, 
and  the  serous  membranes  lining  closed  cavities,  such 
as  the  pleural,  pericardial,  peritoneal,  and  synovial 
membranes. 

The  secretion  from  the  various  epithelial  cells 
lining  mucous  membranes  possesses  different  com- 
position, according  to  the  locality.  It  is  called  mucus, 
a  pale,  semitransparent,  alkaline  fluid  containing 
white  cells  and  epithelial  cells.  Chemically  it  consists 
of  water,  mineral  salts,  and  a  protein  mucin.  Most 
of  the  mucus  is  secreted  by  the  goblet  cells.  Mucus 
is  classified  according  to  where  secreted,  as  nasal, 
bronchial,  vaginal,  urinary,  and  gastro-intestinal. 

The  serous  membranes  are  practically  large  lymph 


292  SECRETION 

spaces  and  the  contained  fluid  is  practically  lymph. 
It  diminishes  friction  when  the  organs  they  enclose 
rub  against  one  another. 

Synovial  membranes  secrete  a  fluid  resembling  lymph, 
but  it  also  possesses  a  protein — a  mucin-Iike  sub- 
stance, which  renders  it  viscid.  Synovial  membranes 
prevent  friction  between  adjacent  surfaces  of  bone 
entering  into  the  formation  of  joints. 

The  other  secretions  of  the  body,  as  the  aqueous 
humor  of  the  eye,  gastric  secretions,  etc.,  will  be 
described  under  the  physiology  of  the  parts. 

THE  SECRETING  GLANDS 

These  are  a  group  of  cells  given  ofl'  as  a  pouch  from 
the  mucous  membrane  or  skin,  and  communicating 
with  the  lining  membrane  or  surface  the  secretion 
is  to  act  upon  by  means  of  an  open  passageway, 
called  a  duct.  Their  epithelial  cells  vary  in  their 
structure  and  function  dependent  on  their  location. 
The  epithelial  cells  of  the  secretory  glands  are  sur- 
rounded by  a  net-work  of  blood  capillaries,  lymph 
vessels,  and  nerves;  the  nerves  are  in  direct  connec- 
tion with  the  epithelial  cells  and  bloodvessels. 

How  these  epithelial  cells  absorb  from  the  lymph 
and  blood  plasma  their  essential  constituents  of  the 
secretions  and  change  them  into  their  difl'erent  chemic 
and  physiologic  fluids  is  not  definitely  known,  except 
that  they  are  the  result  of  metabolic  processes  going 
on  within  the  cells. 

All  secretory  glands  are  controlled  by  nerve  centres 
situated  in  the  central  nerve  system.  Normal 
secretions  of  glands  are  brought  about  by  a  reflex 
action.  In  all  reflexes  there  must  be  a  sensitive 
surface  to  receive  the  impression  (skin,  mucous  mem- 
brane, etc.),  an  afferent  nerve  (one  which  transmits 
the  impression  to  the  centres  in  the  brain),  an  efferent 
nerve   (one  which   transmits  the  return   stimulus  to 


THE  SECRETING  GLANDS  293 

a  responsive  organ — in  this  case  the  cells  of  the  secre- 
tory organ  or  gland). 

The  active  discharge  of  the  secretion  from  the 
cells  is  interrupted  by  periods  of  rest,  during  which 
time,  if  they  be  examined  under  the  microscope,  after 
the  absorption  of  lymph,  they  will  show  accumula- 
tions within  themselves  of  their  characteristic  prod- 
ucts as  globules  of  mucin  —  granules  which  are  the 
basic  formation  of  the  digestive  ferments  or  enzymes, 
granules  of  glycogen,  globules  of  fat,  sugar,  and 
protein,  as  in  the  case  of  the  mammary  gland. 

Excretion  is  a  process  similiar  to  secretion,  the  only 
difference  being  that  the  fluids  removed  are  the 
waste  products  from  the  cells  formed  as  a  result  of 
metabolism. 

The  Mammary  Glands. — These  are  accessory  to 
the  reproductive  system  and  secrete  the  milk.  They 
are  two  rounded  eminences,  one  on  each  side  of  the 
thorax,  between  the  sternum  and  axilla  and  the 
third  and  seventh  ribs.  Just  below  the  centre  is  a 
conical  eminence,  the  nipple,  which  is  dark,  and  is 
surrounded  by  a  pinkish  areola  which  darkens  in 
pregnancy.  It  presents  the  orifices  of  the  lactiferous 
ducts,  and  consists  of  vessels  mixed  in  with  plain 
muscular  fibers,,  and  by  friction  may  be  made  to 
undergo  erection. 

The  mamma  consists  of  a  number  of  lobes  separated 
by  fibrous  tissue  and  some  adipose  tissue.  The  lobes 
are  divided  and  subdivided  into  smaller  lobules, 
which  are  in  turn  made  up  of  alveoli.  Each  lobe  has 
an  excretory  (galactophorous)  duct,  and  these,  about 
sixteen  in  number,  converge  to  the  areola,  there 
dilating  into  ampullae  or  sinuses.  TJiey  then  become 
smaller  again,  and  surrounded  by  areolar  tissue  and 
vessels,  pass  through  the  nipple  to  empty  on  the 
surface  by  separate  orifices. 

Milk. — Milk  as  obtained  from  the  breast  during 
active   secretion   or  lactation   is   an   opaque,   bluish- 


294 


SECRETION 


white  fluid,  without  any  oder,  sweetish  in  taste, 
alkaHne  in  reaction,  and  has  a  specific  gravity  of 
from  1.025  to  1.040.  Examined  microscopically  it 
presents  a  clear  fluid  called  the  plasma,  which  holds 
in   suspension   great   numbers   of   oil   globules.     The 


Fig.  108 


Lactiferous 
duct. 


Lobule. 


Ampulla. 


Loculi  i))  connective  tissue. 


Dissection  of  the  lower  half  of  the  female  breast  during  the  period  of 
lactation.     (From  Luschka.) 


amount  of  milk  secreted  each  day  by  a  healthy  woman 
averages  about  1200  c.c.  Milk  is  the  most  important 
of  the  animal  foods,  containing  all  the  elements 
necessary  to  properly  nourish  and  develop  the  body, 
and  is  used  as  a  food. 


THE  SECRETING  GLANDS  295 

Differences  in  chemical  composition  of  human  and 
cows'  milk  (Holt): 

Woman's  milk  Cows'  milk 

average  average 

per  cent  per  cent. 

Fat 4.00  4.00 

Sugar 7.00  4.50 

Proteins 1.50  3.50 

Salts 0.20  0.75 

Water 87.30  87.25 

100.00  100.00 

By  the  above  it  will  be  seen  that  cows'  milk  has  an 
excess  of  proteins  and  salts,  and  is  deficient  in  sugar. 

The  secretion  of  milk  is  influenced  by  emotional 
states,  both  as  to  quantity  and  quality,  due  to  some 
connection  between  the  nerve  centres  and  the  gland 
cells. 

Colostrum. — This  is  the  first  fluid  secreted  by  the 
breasts  after  the  birth  of  the  infant.  It  is  a  liquid 
which  resembles  milk,  and  contains  epithelial  cells, 
fat  globules,  colostrum  corpuscles.  Colostrum  is 
richer  than  the  milk,  containing  more  lactose  and 
inorganic  salts.  According  to  some  authors  it  contains 
compounds  which  act  as  a  laxative  to  the  newborn. 

The  Liver  (Hepar). — Description  of  the  Liver. — The 
liver  is  the  largest  gland  of  the  body,  and  fills  the 
entire  hypochondrium,  the  greater  portion  of  the 
epigastrium,  sometimes  extending  into  the  left  hypo- 
chondrium. It  weighs  from  50  to  60  ounces  in  the 
male;  40  to  50  ounces  in  the  female.  Constitutes 
one-eighteenth  of  the  body  weight  in  the  adult,  and 
one-thirty-sixth  of  the  body  weight  in  the  fetus.  It 
measures,  transversely,  from  8  to  9  inches;  antero- 
posterior, 4  to  5  inches,  and  vertically,  near  its  right 
surface,  about  6  or  7  inches.  Its  specific  gravity  is 
1.05. 

The  liver  presents  a  superior  surface  which  includes 
the  right  and  left  lobes;  an  inferior  surface,  including 
the  right,  left,  caudate,  spigelian,  and  quadrate  lobes; 


296 


SECRETION 


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THE  SECRETING  GLANDS  297 

anterior    and    posterior   surfaces    ('()ini)rising   the    right 
and  left  lol^es;  a  lateral  surface  of  the  right  lobe,  only. 

It  has  an  inferior  border  or  margin  which  is  thin  and 
sharp,  and  notched  opposite  the  falciform  ligament, 
for  the  round  ligament  (umbilical  notch),  and  opposite 
the  cartilage  of  the  ninth  rib  by  a  second  notch  for 
the  fundus  of  the  gall-bladder. 

The  left  extremity  of  the  inferior  margin  of  liver  is 
thin  and  flattened  from  above  downward. 

The  ligaments  of  the  liver  are  all  peritoneal  folds, 
except  the  round  ligament,  which  is  a  fetal  remnant 
of  the  umbilical  vein.  The  ligaments  hold  the  liver 
in  position,  and  are  as  follows: 

Falciform  or  suspensory.  Left  lateral. 

Coronary.  Round. 

Right  lateral. 

The  lobes  of  the  liver  are  also  five  in  number.  The 
right  is  the  largest,  being  six  times  as  large  as  the 
left.  The  left  lobe  is  flattened,  lies  in  the  epigastrium, 
and  is  in  relation  below  with  the  stomach.  The  lobus 
quadratus  is  on  the  under  surface  of  the  right  lobe. 
The  Spigelian  lobe  lies  behind  and  above  the  preceding. 
The  caudate  lobe,  or  tubercidum  caudatum,  runs  outward 
from  the  base  of  the  Spigelian  lobe  to  the  under  surface 
of  the  right  lobe. 

The  fissures  of  the  liver  are  five.  The  longitudinal 
separates  the  right  and  left  lobes.  The  fissure  of  the 
ductus  venosus  is  the  part  of  the  longitudinal  fissure 
behind  the  transverse.  The  transverse  is  the  point 
of  exit  (hepatic  ducts)  and  entrance  of  the  portal  vein, 
hepatic  arteries,  nerves,  and  lymphatic  vessels.  The 
fissure  for  the  gall-bladder  is  on  the  under  surface  of 
the  right  lobe,  parallel  to  the  longitudinal  fissure,  sepa- 
rated from  it  by  the  quadrate  lobe.  The  fissure  for 
the  inferior  vena  cava,  sometimes  a  complete  canal,  lies 
to  the  right  of  the  Spigelian  lobule. 

The  Structure  of  the  Liver. — It  is  covered  by  a  serous 
layer  derived  from  the  peritoneum,  except  the  posterior 


298  SECRETION 

surface,  which  is  in  relation  with  the  diaphragm  for 
about  3  inches,  included  between  the  reflections  of  the 
coronary  ligaments.  Beneath  this  serous  covering  is 
a  fibrous  or  areolar  capsule  (capsule  of  Glisson),  which 
passes  into  the  transverse  fissure  around  the  vessels 
and  blends  with  the  areolar  tissue  which  holds  the  liver 
lobules  together. 

Fig.  110 


Triinlc  of  infralobn 
vein. 


.ntralobnlar  rein 


Horizontal  section  of  injected  liver  (dog). 

The  lobules  compose  the  main  mass  of  the  liver 
substance,  and  consist  of  irregular  chains  of  hepatic 
cells,  which  secrete  the  bile,  and  are  surrounded  by  a 
capillary  net-work  of  intralobular  veins,  which  are  the 
minute  terminations  of  the  portal  vein;  they  course 
toward  the  centre  of  the  lobule,  opening  into  a 
central  intralobular  vein;  also  small  arteries,  branches 
of  the  hepatic  artery,  lie  between  the  cells. 

In  addition,  within  the  chain  of  cells  are  the  minute 
biliary  ducts,  or  capillaries,  which  are  the  commence- 
ment of  the  hepatic  duct  that  conveys  the  bile  formed 


THE  SECRETING  GLANDS  299 

by  the  liver  cells  to  the  intestinal  canal  and  gall- 
bladder. 

The  Functions  of  the  Liver. — (1)  The  liver  secretes 
the  bile;  (2)  produces  and  stores  glycogen  until  needed 
to  aid  in  the  nutrition  of  the  tissues;  (3)  aids  in  the 
formation  and  excretion  of  urea.  The  production  of 
bile  and  its  physiologic  actions  have  been  described. 
(See  Part  Played  by  the  Bile  in  Digestion,  page  281.) 

The  Formation  and  Function  of  Glycogen. — Glycogen  is 
derived  from  the  dextrose  resulting  from  the  action  of 
the  intestinal  juices  upon  the  food.  It  represents  the 
products  of  the  carbohydrates  absorbed  as  dextrose 
and  carried  in  the  blood  by  the  branches  of  the  portal 
vein  to  the  liver,  when  it  undergoes  chemical  changes, 
due  to  the  action  of  the  liver  cells,  and  is  deposited 
as  a  non-diffusible  body.  Glycogen  is  stored  in  the 
liver  until  needed  by  the  body  tissues. 

The  Formation  of  Urea. — Urea  is  believed  to  be 
produced  and  excreted  by  the  liver  cells.  It  is  formed 
from  ammonium  salts,  as  carbonate,  lactates,  which 
are  formed  as  a  result  of  tissue  metabolism  upon  the 
proteins  contained  in  the  food  we  eat,  and  these 
salts  are  absorbed  from  the  tissues  or  from  the  intes- 
tines, and  conveyed  by  the  blood  to  the  liver  cells, 
where  they  are  converted  into  urea  and  eliminated  as  a 
waste  product.  It  is  excreted  by  the  kidneys  and 
found  in  the  urine. 

The  Gall-bladder. — This  is  a  pear-shaped  sac  lying 
in  the  impression  of  the  right  lobe  of  the  liver.  It  is 
the  reservoir  for  the  bile.  It  is  4  inches  long  and  1| 
inches  broad,  holding  8  to  12  drams,  and  is  held  in 
place  by  areolar  tissue  and  the  peritoneum.  Its 
relations  are  as  follows:  Above,  liver;  below,  ascending 
duodenum,  pyloric  end  of  stomach,  hepatic  flexure  of 
colon;  in  front,  abdominal,  wall  (ninth  or  tenth  costal 
cartilages) . 

The  hepatic  duct  is  formed  by  the  junction  at  an 
obtuse   angle   of    a    branch   from    each    lobe   of    the 


300 


SECRETION 


liver  and  runs  downward  and  to  the  right  for  nearly 
2  inches  and  joins  the  cystic  duct  to  form  the  common 
bile  duct.    The  cystic  duct  of  the  gall-bladder  is  1 1  inches 


Fig.  Ill 


COMMON 
DUCT 


GALL- 
BLADDER 


The  gall-bladder  and  bile  ducts,  opened  up.    (Spalteholz.) 


long,  and  descends  tow^ard  the  left  and  joins  the  above 
as  described.  The  common  bile  duct  is  nearly  3  inches 
long  and  3  lines  in  diameter.  It  runs  along  the  right 
border  of  the  lesser  omentum,  behind  the  first  part 


THE  SECRETING  GLANDS 


301 


of  the  duodenum,  and  between  the  pancreas  and 
descending  duodenum,  then  to  the  right  of  the  pan- 
creatic duct,  with  which  it  communicates  by  a  common 
orifice,  at  the  summit  of  a  papilla  situated  just  below 
the  middle  of  the  inner  wall  of  the  second  portion  of 
the  duodenum.  The  cystic  artery  and  veins  comprise 
the  blood-supply  of  the  gall-bladder  and  its  duct. 

Fig.  112 


The  pancreas  and  its  relations.     (Gray.) 


The  Pancreas. — The  pancreas  is  a  compound  race- 
mose gland,  of  a  pinkish-white  color.  Situated  at  the 
back  of  the  epigastrium  and  left  hypochondrium ; 
connected  to  the  posterior  abdominal  wall  by  connected 
tissue,  and  lies  posterior  to  the  stomach  and  behind 
the  peritoneum.  It  is  5  or  6  inches  long;  its  breadth 
is  1|  inches;  its  thickness  J  to  1  inch,  being  greater 
at  its  right  extremity  and  upper  border.  The  pancreas 
is  divided  into  a  head,  a  neck,  a  body,  and  a  tail. 

The  duct  of  the  pancreas  is  called  the  pancreatic 
duct    or   canal   of   Wirsung.      It   extends   transversely 


302  SECRETION 

through  the  substance  of  the  gland  to  drain  the 
lobules  by  means  of  small  ducts  which  open  into  it. 
Increasing  in  size  it  reaches  the  neck,  passes  down- 
ward, backward,  and  obliquely  to  the  right,  piercing 
the  muscular  and  mucous  coat  of  the  second  portion 
of  the  duodenum  where  it  opens  into  the  ampulla  of 
Vater,  common  to  it  and  the  bile  duct;  the  latter  opens 
into  the  canal  of  the  duodenum. 

The  Structure  of  the  Pancreas. — It  is  similar  in 
structure  to  the  salivary  glands,  consisting  of  numbers 
of  lobules,  forming  lobes,  and  all  held  together  by 
connective  tissue.  Each  lobule  contains  one  of  the 
branches  of  the  main  duct,  which  terminates  in  the 
grape-like  alveoli.  The  alveoli  are  lined  by  cylindric 
cells,  which  differ  in  their  appearance.  They  are 
divided  into  a  central  set,  in  the  end  of  the  alveoli, 
which  are  dark  and  granular,  and  a  peripheral  set, 
in  the  outside  of  the  former,  which  are  clear.  During 
digestion  the  granular  area  becomes  broader  and  the 
cells  show  an  increase  in  granules;  in  the  interval  of 
rest  following  active  digestion  the  clear  zone  increases 
in  width,  showing  an  absence  of  granules. 

The  Areas  or  Islands  of  Langerhans  are  groups  of 
globular  cells  arranged  in  columns  situated  between 
the  alveoli;  surrounded  by  connective  tissue,  which 
separates  them  from  the  alveoli  and  each  other.  The 
connective  tissue  contains  large,  twisted,  capillary 
bloodvessels.  These  groups  of  goblet  cells  are  supposed 
to  secrete  an  internal  secretion,  which  is  absorbed  by 
the  blood  and  carried  to  the  different  tissues.  Metab- 
olism of  the  carbohydrates  is  interfered  with,  if  any 
diseased  condition  or  removal  of  the  pancreas  takes 
place.  The  secretion  from  the  cells  of  the  alveoli, 
on  the  other  hand,  secretes  the  pancreatic  juice. 

The  pancreatic  secretion^  leaves  the  pancreas  by 
way  of  the  duct  of  Wirsung;  it  is  supposed  to  create 

^  See  page  279  for  action  of  pancreatic  secretion  during  digestion. 


THE  SECRETING  GLANDS 


303 


an  internal  secretion  which  regulates  the  production 
of  glycogen  by  the  liver,  thus  possessing  both  an 
internal  and  external  secretory  function. 


Fig.  113 
Interlobular  duct. 


Section  of  human  pancreas,  showing  pancreatic  islands.     (Radasch.) 


Ductless  Glands. — The  ductless  glands  of  the  body 


are: 


Thyroid. 
Parathyroids. 
Spleen. 
Carotid. 


Thymus. 

Suprarenal  capsules. 
Pituitary  body. 
Coccygeal. 


The  above  glands  aid  in  the  nutrition  of  the  whole 
body  as  well  as  in  that  of  individual  organs  by  means 
of  an  internal  secretion  which  is  absorbed  by  the  blood 
and  lymph  streams.    This  material,  derived  from  the 


304  SECRETION 

circulation,  is  changed  within  the  gland  by  some 
unknown  phenomena  and  secreted  by  the  cells  of 
the  ductless  glands  to  be  taken  into  the  blood  and 
lymph  direct,  and  thus  aid  in  promoting  the  metab- 
olism of  the  body.     They  possess  no  ducts. 

The  Thjrroid  Gland. — This  is  a  very  vascular  organ, 
situated  at  the  front  of  the  neck,  overhanging  the 
upper  rings  of  the  trachea  and  laterally  extending  as 
high  as  the  oblique  line  on  the  alse  of  the  thyroid 
cartilage,  and  as  low  as  1  inch  above  the  upper  border 
of  the  sternum,  when  the  head  is  extended.  It  weighs 
about  1  ounce;  slightly  heavier  in  the  female.  It 
has  three  lobes — two  lateral  connected  by  an  isthmus ; 
and  one  third  or  middle  lobe.  It  is  firmly  attached  to 
the  cricoid  cartilage  and  posterior  fascia  of  the  trachea 
by  two  lateral  or  suspensory  ligaments  and  its  lobes 
and  isthmus  are  enclosed  within  a  fibrous  capsule 
derived  from  the  pretracheal  portion  of  the  deep 
fascia  of  the  neck. 

The  isthmus  lies  on  the  second  and  third  ring  of 
the  trachea,  and  measures  about  J  inch  in  breadth 
and  depth. 

The  functions  of  the  thyroid  are  not  thoroughly 
understood.  It  is  an  established  fact,  however,  that 
when  the  gland  is  secreting  more  or  less  than  the 
normal  quantity,  changes  in  development  arise  as  a 
result  of  some  physiologic  disturbance  interfering 
with  the  general  metabolism  of  the  body;  as  cretinism, 
a  condition  occurring  in  infants  and  children  as  a  result 
of  a  congenital  absence  or  arrested  development  of  the 
gland;  myxedema,  a  condition  (occurring  in  adults)  of 
the  skin  in  which  it  becomes  thickened,  giving  rise  to  a 
change  in  the  patient's  expression,  due  to  the  face  becom- 
ing broader,  swollen,  and  flattened.  The  mind  is  dull, 
the  subject  is  almost  idiotic  as  regards  the  mental 
condition.  Myxedema  is  due  to  atrophy  or  some 
pathologic  change  taking  place  in  the  gland  which 
interfered  with  its  normal  secretion;  removal  of  the 


THE  SECRETING  GLANDS  305 

gland  by  operation  gives  rise  to  a  similar  condition, 
called  cachexia  strumipriva;  an  increase  in  the  secretion 
from  the  thyroid  gland  causes  a  condition  characterized 
by  protrusion  of  the  eye-balls — the  patient's  expression 
is  staring  and  frightened — palpitation  of  the  heart 
and  enlargement  of  the  gland,  termed  exophthalmic 
goitre  or  Graves'  disease.  An  enlargement  of  the 
thyroid  gland,  which  is  gradually  progressive,  can 
be  seen  in  the  necks  of  people  living  in  or  coming 
from  certain  localities  where  the  diseased  condition 
is  due  to  the  drinking  water  containing  lime;  this  is 
termed  ordinary  goitre. 

The  Parathyroid  Glands. — These  are  small,  reddish- 
brown  bodies,  composed  of  masses  of  cells,  arranged 
in  a  more  or  less  reticular  manner  with  numerous 
intervening  bloodvessels.  They  are  usually  found 
one  on  either  side  (the  superior)  at  the  level  of  the 
lower  border  of  the  cricoid  cartilage,  behind  the 
junction  of  the  pharynx  and  esophagus,  and  in  front 
of  the  prevertebral  fascia.  The  lower  are  just  below 
the  lower  edge  of  the  lateral  lobe  one  on  either  side. 
There  are  usually  four,  but  may  be  only  three,  or  again, 
as  many  as  six  or  eight.     Their  location  is  variable. 

The  functions  of  the  parathyroids  have  not  been 
sufficiently  established  to  warrant  a  description 
within  these  pages.  However,  their  removal  from 
animals  has  given  rise  to  tetany,  characterized  by 
spasmodic  contractions  and  paralyses  of  certain 
groups  of  muscles,  convulsive  seizures,  and  death. 

Spleen. — The  spleen  is  the  largest  of  the  ductless 
glands.  It  is  found  in  the  left  hypochondrium,  entirely 
surrounded  by  peritoneum,  except  around  the  hilum, 
which  attaches  it  to  the  fundus  of  the  stomach  (the 
gastrosplenic  omentum).  It  is  purplish  in  color, 
oblong,  flattened,  tetrahedral  form,  soft,  of  a  very 
friable  consistency,  and  highly  vascular.  It  measures 
5  inches  in  length,  2  to  3  inches  in  width,  and  1  to  IJ 
inches  in  thickness  at  the  centre.  It  weighs  6|  ounces, 
20 


306  SECRETION 

The  spleen  is  attached  to  the  stomach  by  the 
gastrosplenic  omentum.  The  lienorenal  ligament  is  a 
peritoneal  fold,  which  attaches  it  to  the  upper  pole  of 
the  left  kidney,  and  the  phrenocolic  assists  to  support 
it  by  its  attachment  to  the  diaphragm. 

The  spleen  when  seen  under  the  microscope  shows 
a  capsule  of  fibrous  tissue  which  sends  off  slips  or 
trabeculae  from  its  under  surface;  these  spread  out 
and  form  a  connective-tissue  supporting  frame-work 
for  the  contents  of  the  organ,  which  consists  of  a 
dark  red  semifluid  mass  called  the  splenic  pulp,  filling 
the  spaces  between  the  fibrous  tissue.  Microscopically 
the  splenic  pulp  is  seen  to  consist  of  adenoid  tissue, 
rich  in  leukocytes  or  white-blood  cells,  arranged  in 
small  groups  throughout  the  pulp,  called  Malpighian 
corpuscles;  red  corpuscles  are  also  present  in  the  pulp. 

The  Functions  of  the  Spleen. — Owing  to  the  numbers 
of  red  cells  seen  in  the  splenic  pulp  undergoing  all 
stages  of  disintegration,  it  has  been  concluded  that 
the  spleen  aids  in  the  destruction  of  red  cells;  another 
theory  is  based  on  the  presence  of  the  large  quantity 
of  white  cells  within  the  Malpighian  corpuscles,  that 
the  spleen  is  the  chief  centre  for  the  production  of 
white  cells,  and  thus  contributes  to  the  formation  of 
the  blood. 

The   spleen  is  larger   in   childhood   than   old   age; 

it  is  enlarged  during  and  after  digestion.     In  typhoid 

fever  and  malaria  a  marked  increase  can  be  noted; 

I        .  .  . 

also  in  various  blood  diseases. 

Thymus  Gland. — The  thymus  gland  is  a  temporary 
organ,  attaining  its  full  size  at  the  end  of  the  second 
year  and  gradually  shrinking  until  puberty,  when 
it  entirely  disappears.  Consists  of  two  lateral  lobes 
placed  in  close  contact  along  the  median  line.  It 
is  found  in  the  superior  mediastinum,  covered  by  the 
sternum  and  the  origins  of  the  sternohyoid  and  sterno- 
thyroid muscles;  below,  it  rests  upon  the  pericardium, 
niul  separated  from  the  arch  of  the  aorta  and  great 


THE  SECRETING  GLANDS  307 

vessels  by  fascia.  In  the  neck  it  lies  on  the  front 
and  sides  of  the  trachea  beneath  the  sternohyoid 
sternothyroid  muscles. 

Suprarenal  Glands. — The  suprarenal  glands  are  two 
flattened  bodies,  of  a  yellowish  color,  found  in  the 
epigastrium,  lying  behind  the  peritoneum,  and  above 
and  in  front  of  the  upper  extremity  of  each  kidney. 
They  are  triangular  in  shape,  H  to  nearly  2  inches  in 
length,  less  in  width,  and  J  of  an  inch  in  thickness. 

The  Functions  of  the  Suprarenal  Glands. — They 
secrete  a  substance,  termed  adrenalin  (takamine, 
Aldrich)  or  epinephrin  (Abel),  which  is  absorbed 
by  the  blood,  and  stimulates  to  increased  activity 
the  muscle  fibers  of  the  heart  and  arteries,  and  thus 
aids  in  maintaining  the  normal  blood-pressure.  Dis- 
ease of  the  suprarenal  glands  causes  a  bronzing  of 
the  skin  and  mucous  membranes  with  disturbances 
of  nutrition,  muscular  weakness,  and  anemia.  Gradu- 
ally the  heart  becomes  weak;  the  pulse  is  soft  and 
feeble,  indicating  a  general  reduction  in  blood-pressure 
from  interference  with  the  secretion  of  the  active 
physiologic  material  from  the  cells  of  the  gland. 
Addison's  disease  is  the  name  applied  to  this  condition, 
as  he  first  described  the  disease. 

The  Pituitary  Body  (Hypophysis). — The  pituitary 
body  is  a  small  glandular  body  situated  at  the  base 
of  the  brain,  lodged  in  the  sella  turcica  of  the  sphenoid 
bone.  It  is  divided  into  an  anterior  and  posterior 
lobe;  the  former  is  reddish  in  color,  is  larger  than  the 
posterior  lobe,  and  is  derived  from  an  invagination  of 
the  epiblast  of  the  mouth  cavity,  and  shows  micro- 
scopically gland  tissue;  the  posterior  lobe  is  yellowish 
gray  in  color,  and  represents  an  outgrowth  from 
the  brain.  It  is  connected  by  a  thin  slip  to  the 
infundibulum. 

The  functions  of  the  pituitary  are  still  under  inves- 
tigation; however,  it  has  been  proved  by  experiment 
that  an  injection  of  the  extract  made  from  the  internal 


308  SECRETION 

secretion  of  this  gland  will  cause  an  increase  in  the 
force  of  the  heart-beat  and  a  rise  in  blood-pressure 
by  stimulating  the  arterioles.  According  to  Howell, 
the  extract  given  intravenously  from  the  posterior  lobe 
will  cause  a  rise  in  blood-pressure  and  slow  the  heart- 
beat, the  extract  from  the  anterior  lobe  being  negative 
as  to  its  effect  on  the  circulatory  and  respiratory 
organs.  Disease  of  the  pituitary  body  will  give  rise 
to  the  condition  of  acromegalia,  in  which  there  is  a 
marked  enlargement  of  the  bones  of  the  face  and 
extremities.  When  diseased  in  early  life  it  is  respon- 
sible for  the  progressive  changes,  characterized  by 
extreme  growth  of  the  body,  termed  gigantism;  also 
a  marked  increase  of  fatty  tissue. 

Carotid  Glands. — The  carotid  glands  or  bodies  are 
small  reddish-brown  bodies,  oval  in  shape,  their  long 
diameter  measuring  i  of  an  inch.  They  are  found  in 
the  cervical  region,  at  the  bifurcation  of  the  common 
carotid  artery  into  the  internal  and  external  carotid 
trunks. 

Coccygeal  Gland. — The  coccygeal  gland  or  body, 
or  Luschka's  gland,  is  as  large  as  a  millet-seed,  found 
at  the  tip  of  the  coccyx.  It  is  connected  with  middle 
sacral  artery. 

QUESTIONS 

1.  Give  the  difference  between  an  external  and  internal  secretion. 

2.  Name  some  of  the  external  secretions. 

3.  How  are  secretions  utilized  by  the  tissues  of  the  body? 

4.  Name  the  secreting  membranes  of  the  body. 

5.  Name  the  organs  of  internal  secretion. 

6.  Give  the  general  arrangement  of  the  structures  seen  in  a 
secretory  gland. 

7.  By  what  structure  does  a  secreting  gland  communicate  with 
a  membrane  upon  which  its  secretion  is  poured  out? 

8.  What  part  does  the  nerve  system  play  in  regard  to  gland 
secretion? 

9.  What  is  excretion? 

10.  Describe  the  structure  of  a  mammary  gland. 

11.  Is  human  milk  alkaline  or  acid  in  reaction? 

12.  Docs  milk  contain  oil  globules? 


QUESTIONS  309 

13.  How  much  milk  is  secreted  every  day  by  the  mammary  glands 
in  a  healthy  woman? 

14.  Give  the  chemical  composition  of  milk. 

15.  How  does  woman's  milk  differ  from  cows'  milk? 

16.  What  is  colostrum?    Give  its  function. 

17.  Which  is  the  largest  gland  of  the  body? 

18.  How  much  does  the  liver  weigh? 

19.  How  many  lobes  has  it? 

20.  What  structures  pass  out  of  and  enter  the  transverse  fissure 
of  the  liver? 

21.  Give  the  location  of  the  liver  in  the  abdominal  cavity. 

22.  What  is  the  serous  membrane  surrounding  the  liver  called? 
The  fibrous  capsule? 

23.  What  microscopic  structures  are  seen  in  the  liver  lobules? 

24.  Name  the  functions  of  the  liver. 

25.  How  is  glycogen  formed?     Where  is  it  stored  in  the  body 
chiefly? 

26.  Is  urea  a  waste  product  resulting  from  metabolism?     Which 
organs  excrete  it? 

27.  What  is  the  function  of  the  gall-bladder?     Name  its  duct. 

28.  Where  is  it  located? 

29.  What  ducts  form  the  common  bile  duct? 

30.  Where  does  the  common  bile  duct  drain? 

31.  How  long  is  the  cystic  duct?     The  common  bile  duct? 

32.  To  which  variety  of  glands  does  the  pancreas  belong? 

33.  Give  the  dimensions  of  the  pancreas. 

34.  Name  the  duct  of  the  pancreas.     Which  portion  of  the  duo- 
denum does  it  open  into? 

35.  What  is  the  opening  in  the  duodenum  for  the  common  bile 
and  pancreatic  duct  called? 

36.  How  does  the  pancreatic  secretion  leave  the  pancreas? 

37.  Name  the  organs  of  internal  secretion. 

38.  Which  one  of  the  ductless  glands  is  the  largest? 

39.  Give  its  dimensions  and  weight. 

40  How  is  the  spleen  attached  to  the  stomach?    The  left  kidney? 
The  diaphragm? 

41.  Where  are  the  suprarenal  glands  located  in  the  abdominal 
cavity? 

42.  Name  their  functions? 


CHAPTER  XV 

THE    FACTORS    ESSENTIAL    TO    THE    PRO- 
DUCTION OF  BODY  TEMPERATURE 
OR  HEAT 

The  human  body  maintains  an  even  temperature 
during  life,  due  to  the  results  of  chemic  changes  going 
on  within  the  tissues  and  organs  of  the  body  as  a 
result  of  metabolism.  These  changes  result  from  the 
processes  of  oxidation  taking  place  in  the  cells  of  the 
body  by  the  union  of  oxygen  with  the  elements 
carbon  and  hydrogen,  contained  within  the  food  we 
eat,  either  before  or  after  they  become  constituents  of 
the  tissues.  During  metabolism  of  the  body  the  food 
is  again  broken  up  into  simple  compounds,  as  carbon 
dioxide,  w^ater,  and  urea,  which  evolve  a  large  portion 
of  their  energy  as  heat  and  mechanic  activity. 

The  body  is  continually  giving  off  heat  called 
heat  dissipation,  and  this  heat  dissipation  must  be 
replaced  by  an  equal  amount  of  heat  liberation, 
called  heat  production,  by  the  tissues  as  a  result  of 
metabolism,  else  the  even  temperature  of  the  body 
would  not  be  maintained,  as  is  necessary  for  the 
normal  action  of  the  physiologic  processes  of  the  body. 

Heat  Production. — Heat  production  is  derived  from 
the  formation  of  carbon  dioxide,  urea,  and  water,  as 
a  result  of  oxidation  of  the  tissues  by  the  union  of 
oxygen  with  the  carbon  and  hydrogen  of  the  food. 
And  mechanically  each  of  the  following  actions 
contribute  to  the  production  of  heat:  Contraction 
of  muscles,  during  the  secretions  of  glands,  the  force 
exhibited  by  the  nerve  system  in  producing  its  func- 
tions of  receiving  and  conveying  impulses  throughout 


HEAT  VALUES  OF  FOOD  311 

the  body  to  accomplish  the  various  actions  essential 
to  the  life  of  the  individual. 

Heat  Dissipation. — Heat  is  given  off  by  warming 
the  food  and  liquids  consumed,  to  the  temperature  of 
the  body;  in  warming  the  air  we  breathe  to  the  body 
temperature;  in  the  evaporation  of  water  from  the 
lungs  and  skin;  in  the  skin  it  is  given  off  by  the  pro- 
cesses of  radiation  and  conduction. 

The  quantity  of  heat  essential  to  the  maintenance 
of  the  body  temperature  and  the  quantity  liberated 
is  determined  experimentally  by  a  study  of  the  heat 
values  of  different  foods;  another  method  is  by 
means  of  an  apparatus  called  a  colorimeter,  in  which 
is  collected  and  measured  the  heat  given  off  as  a 
result  of  oxidation  of  the  food  within  and  given  off 
from  the  body  daily. 

Heat  Values  of  Food. — By  the  first  method  1  gram 
of  food  is  burned,  the  hydrogen  and  carbon  of  the 
food  is  chemically  converted  into  carbon  dioxide  and 
water  as  a  result  of  oxidation,  and  during  this  change 
heat  is  given  off  and  collected  which  the  experiment  has 
proved  will  raise  the  temperature  of  a  given  amount 
(1  kilogram)  of  water.  The  amount  of  heat  evolved 
is  expressed  in  gram  or  kilogram,  degrees  or  calories. 

A  calorie  is  the  amount  of  heat  necessary  to  raise 
1  gram  of  water  1°  C.  It  has  been  demonstrated 
that  certain  foods  produce  far  more  heat  than  others 
(expressed  in  calories),  and  hence  more  or  less  heat 
will  be  dissipated,  and  an  increase  or  decrease  in 
energy  will  be  apparent,  dependent  upon  whether 
the  diet  is  rich  in  proteins,  carbohydrates,  or  fats. 
The  carbohydrates  and  fats  are  reduced,  after  being 
absorbed  to  carbon  dioxide  and  water,  the  proteins 
are  changed  to  a  compound^ — urea — with  the  liberation 
of  heat,  expressed  in  calories  as  follows: 

1  gram  of  protein 4.1  calories 

1  gram  of  fat 9.3  calories 

1  gram  of  carbohydrates -.4.1  calories 


312  BODY  TEMPERATURE  OR  HEAT 

Knowing  the  above,  it  is  easy  to  determine  the 
heat  units  or  calories  each  quantity  of  contained 
proteins,  fats,  and  carbohydrates  in  a  diet  will  liberate. 
The  number  of  grams  of  protein  are  multiplied  by 
4.1  calories,  which  one  gram  of  protein  evolves;  the 
number  of  grams  of  fat,  by  9.3  calories,  that  one 
gram  of  fat  evolves;  and  the  number  of  grams  of 
carbohydrates  by  4.1  calories,  the  amount  of  calories 
that  1  gram  of  carbohydrates  liberates.    See  example: 

The  quantity  of  protein  consumed  daily  is 

100  gm.   =  100  X  4.10  or 410  calories 

The    quantity    of    carbohydrates    consumed 

daily  is  500  gm.   =  500  X  4.1  or   .      .      .     2050  calories 

The  quantity  of  fats  consumed  daily  is  50 

gm.   =  50  X  9.3  or 465  calories 

2925  calories 

The  average  number  of  calories  required  by  an 
individual  daily,  to  maintain  an  even  temperature, 
and  promote  the  normal  energy  of  the  body,  is  about 
3000.  Thus  the  heat  dissipated  by  the  body  will 
nearly  equal  the  physiologic  heat  values  of  the  foods 
we  eat. 

The  Temperature  of  the  Body. — The  equalization 
of  the  heat-dissipation  and  heat-production  keeps 
the  body  at  a  standard  temperature.  This  in  olden 
times  w^as  taken  by  physicians  simply  by  laying  the 
hand  on  the  skin.  The  introduction  of  the  clinical 
thermometer  has  allowed  of  a  more  accurate  and 
scientific  means  of  reading  the  temperature.  The 
temperature  of  the  body  varies  in  different  locations, 
due  to  the  chemic  changes  resulting  from  body  metab- 
olism varying  in  their  intensity  and  extent  in  different 
parts  of  the  body.  This  variation  would  be  more 
marked  were  it  not  due  to  the  fact  that  the  blood 
and  lymph  absorbing  the  heat,  evenly  distribute  it 
to  all  parts  of  the  body,  so  that  the  change  in  temper- 
ature amounts  to  only  a  few  degrees. 


QUESTIONS  313 

The  normal  body  temperature  in  the  axilla  is 
98.6°  F.  or  37°  C.  (French).  This  may  be  as  low 
as  97.5°  to  98°  F.  in  the  early  morning,  and  reaching 
to  99°  to  99.3°  F.  in  the  evening,  and  denote  no  abnor- 
mal condition  of  health;  by  mouth,  98.6°  F.  or  37°  C; 
rectum,  100.4°  F.  or  38°  C;  vagina,  100.9°  F.  or 
38.3°  C.  In  infancy  under  six  years  of  age,  99.4°  F. 
or  37.4°  C;  in  the  aged  (sixty  to  eighty  years),  98.2° 
F.  or  36.8°  C. 

QUESTIONS 

1.  How  does  oxidation  of  the  tissues  effect  heat  production? 

2.  What  mechanical  actions  of  the  body  aid  in  heat  production? 

3.  How  is  heat  dissipation  brought  about? 

4.  What  must  occur  in  the  tissues  to  equal  heat  dissipation  in 
order  to  maintain  an  even  body  temperature? 

5.  How  are  heat  values  expressed? 

6.  How  many  calories  will  1  gram  of  protein  produce?  1  gram 
of  fat?     1  gram  of  carbohydrates? 

7.  What  is  a  calorie. 

8.  What  is  the  average  number  of  calories  required  to  maintain 
an  even  temperature  and  promote  the  normal  energy  of  the  body? 

9.  What  relation  should  the  heat  dissipated  by  the  body  bear  to 
the  heat  values  of  the  foods  we  consume? 

10.  Give  the  normal  temperature  when  taken  by  mouth,  axilla, 
and  rectum. 


CHAPTER  XVI 

THE  ANATOMY  AND  PHYSIOLOGY  OF  THE 
URINARY  APPARATUS  (ORGANS);  THE 
SKIN  AND  ITS  APPENDAGES 

THE  URINARY  ORGANS 

.  The  urinary  organs  include  the  kidneys,  which 
secrete  or  excrete  the  urine ;  the  ureters  convey  it  to  the 
bladder,  where  it  is  retained  until  voided  (micturition) ; 
then  the  urethra  which  discharges  it  from  the  body. 

The  Kidneys  (Renes). — The  kidneys  are  situated  in 
the  abdominal  cavity  on  each  side  of  the  vertebral 
column,  resting  on  the  psoas  magnus  and  the  quad-^ 
ratus  lumborum  muscles.  They  are  behind  the  peri- 
toneum and  correspond  to  the  space  included  between 
the  upper  level  of  the  twelfth  thoracic  above,  and 
opposite  the  third  lumbar  vertebra  below.  The  right 
kidney  is  lower  than  the  left.  In  the  female  they  are 
a  little  lower  than  in  the  male. 

Each  is  bean-shaped,  measures  about  4  to  4 J  inches 
in  length,  2|  in  breadth,  and  1  to  IJ  inches  in  thick- 
ness, and  weighs  about  4  to  6  ounces.  They  lie  in  the 
right  and  left  hypochondrium,  the  epigastrium,  and 
the  right  and  left  lumbar  regions. 

Fixation  of  the  Kidney. — The  kidney  is  embedded  in 
a  mass  of  fatty  tissue  (capsule  adiposa)  surrounded  by 
a  fibrous  sheath  named  the  fascia  renalis  continuous 
with  the  subperitoneal  fascia. 

The  Structure  of  the  Kidney. — The  kidney  is  made 
up  of  a  series  of  tubules  supported  by  a  frame-work 
of  connective  tissue,  and  surrounded  by  small  capil- 


THE  URINARY  ORGANS 


315 


laries,   lymphatics,   and   nerves.     On   examining  the 
incised  kidney  its  surface  presents  an  inner  two-thirds, 


Fio.  114 


Posterior  abdominal  wall,  after  removal  of  the  peritoneum,  showing 
kidneys,  suprarenal  capsules,  and  great  vessels.    (Corning.) 


316 


THE  URINARY  APPARATUS 


called  the   medulla,  measuring  |  to 

thickness;   and  an  outer  one-third   called  the  cortex, 

measuring  J  to  J  inch  in  thickness. 


Fia.  115 


COLUMN    OF 
BERTIN 


MEDULLARY 
PYRAMID 


EDULLARY 
PYRAMID 

COLUMN  or 

BERTIN 


Vertical  section  of  kidney,  showing  the  secreting  portion,  the  vessels, 
and  the  beginnings  of  the  ureter.     (Testut.) 


The  Medulla. — This  consists  of  small  pyramids, 
ten  to  twenty  in  number.  The  base  of  each  is 
directed  toward  the  cortex  and  the  apices  point 
toward  the  pelvis  of  the  ureter,  where  they  project 
into  the  calices  of  the  same;  each  calix  receives  one. 


THE  URINARY  ORGANS  317 

two,  or  three  papillae.  Each  papillae  has  a  number 
of  minute  openings  upon  its  apex  for  the  excretory 
ducts  of  the  pyramids;  the  latter  pour  the  urine  into 
the  pelvis  of  the  ureter.  These  orifices  open  into 
tubules  and  are  practically  the  external  outlet  of 
the  uriniferous  tubules.  They  pass  toward  the  base 
of  the  pyramid,  and  within  this  region  are  known  as 
the  tubes  of  Bellini.  Continuing  they  enter  the  cortex, 
where  they  become  enlarged  and  twisted,  and  follow 
an  extremely  tortuous  course  to  turn  backward  into 
the  medullary  portion  for  some  space,  and  are  called 
in  this  position  the  ascending  limb  of  the  loop  of  Henle; 
they  curve  upon  themselves  again,  and,  while  still 
within  the  medullary  portion,  are  known  as  the 
descending  limb  of  the  loop  of  Henle ;  reenter  the  cortex, 
expand  again,  and  becoming  twisted  (convoluted 
tubule),  end  in  an  ovoid  enlargement  termed  Bowman's 
capsule,  in  which  is  a  small  collection  of  bloodvessels — 
the  glomerulus,  or  Malpighian  tuft.  The  capsule  and 
contained  bloodvessels,  the  glomerulus,  constitute 
the  small  reddish  bodies  called  renal  or  Malpighian 
corpuscles,  which  are  scattered  throughout  the  cortex 
of  the  kidney. 

The  Cortex. — This  is  reddish  brown  in  appearance, 
and  lies  just  beneath  the  capsule  of  the  organ.  It 
contains  the  Malpighian  corpuscles.  When  examined 
with  a  lens  it  has  a  light  colored,  ray-like  appearance. 
The  lighter  rays  are  termed  the  medullary  rays,  and 
are  found  by  the  collection  of  uriniferous  tubules  (loops 
of  Henle)  from  the  medullary  portion.  The  darker 
colored  intervening  substance  is  called  the  labyrinth, 
from  its  complexity  of  structure,  and  is  composed  of 
the  Malpighian  corpuscles  and  the  various  loops  of  the 
tubules. 

The  Uriniferous  Tubules. — Microscopic  examination 
of  the  kidney  substance  is  the  only  method  by  which 
the  uriniferous  tubules  can  be  seen  and  understood. 


318  THE  URINARY  APPARATUS 

However,  I  will  endeavor  to  make  as  clear  as  possible 
their  course.  The  tubules  practically  start  in  the  cortex 
as  a  capsule  of  Bowman,  which  surrounds  the  capillaries 
(glomerulus).  The  tubules  run  a  very  irregular  and 
distorted  course,  and  finally  end  in  straight  tubules 
which  pass  through  the  pyramids  to  empty  into  the 
calices  of  the  pelvis  of  the  ureter.  Bowman's  capsule 
is  lined  by  flattened  epithelial  cells  resting  on  a  very 
delicate  basement  membrane.  The  convoluted  por- 
tions of  the  tubules  are  lined  with  cuboidal  epithe- 
lium and  the  loops  of  Henle  contain  more  or  less 
flattened  epithelium. 

The  Ureters. — The  ureters  are  two  tubes,  and  con- 
vey the  urine  from  the  kidney  to  the  bladder.  The 
urine  is  collected  from  several  minor  calices,  ten  to 
twenty  in  number,  which  open  into  the  major  calices; 
the  latter  by  their  junction  form  the  pelvis  or  dilated 
portion  of  the  ureter.  It  is  on  a  line  with  the  first 
lumbar  vertebra. 

The  ureter  proper  is  divided  into  an  abdominal 
portion  (pars  abdominalis)  and  a  pelvic  portion  (pars 
pelvina).  They  are  10  to  12  inches  in  length  and  ^  of 
an  inch  in  diameter.  The  walls  are  from  1  to  2  mm. 
thick. 

The  Urinary  Bladder  (Vesica  Urinaris) .— The  bladder 
is  situated  in  the  pelvic  cavity,  but  in  infancy  and 
when  distended  in  the  adult,  extends  into  the  hypo- 
gastrium.  It  measures  when  moderately  distended, 
5  to  5i  inches  in  length,  4^  in  width,  and  3  inches 
from  before  backward.  It  holds  a  pint  of  urine 
without  discomfort.  The  bladder  presents  a  superior, 
antero-inferior,  and  two  lateral  surfaces;  a  base  or 
fundus,  and  an  apex  or  summit. 

The  interior  of  the  bladder  shows  the  mucous  mem- 
brane thrown  into  rugae,  the  orifices  of  the  ureters,  and 
the  trigone,  also  the  orifice  of  the  urethra,  which  empties 
the"urine  from  the  bladder.     The  ureteral  orifices  are 


THE  URINARY  ORGANS  319 

about  2  inches  apart  when  the  bladder  is  moderately 
distended.  The  trigone  is  a  smooth,  triangular  surface, 
paler  than  the  rest  of  the  mucous  membrane.  It  is 
bounded  at  the  basal  angles  to  the  orifices  of  the  ureters, 
and  the  apex  to  the  internal  urethral  orifice.  The 
ureteral  folds  are  the  prolongations  extending  beyond 
the  ureteral  orifices,  of  the  transverse  ureteral  fold 
containing  muscle  fibers  covered  by  the  mucous 
membrane.  The  internal  urethral  openings  is  sur- 
rounded by  a  circular  fold  of  mucous  membrane, 
called  the  annulus  urethalis. 

The  ligaments  of  the  bladder  are:  true  and  false. 
The  true  are  the  two  anterior,  two  lateral,  and  the 
urachus.  The  false  are  five,  and  consist  of  folds  of 
peritoneum. 

Method  of  Urine  Secretion. — The  urine  contains 
the  waste  products  resultant  from  body  metabolism 
which  are  eliminated  through  the  kidneys,  ureter, 
bladder,  and  urethra. 

Several  theories  have  been  demonstrated  in  regard 
to  how  these  waste  products  pass  from  the  blood  to 
the  urine.  However,  the  two  accepted  methods  of 
urine  secretion  or  excretion  are  based  on  the  principles 
of  filtration  and  secretion. 

The  uriniferous  tubules  as  described  above  com- 
mence as  the  capsule  of  Bowman,  which  surrounds 
a  collection  of  capillaries  (glomerulus).  Bowman's 
capsule  is  simply  an  indentation  of  the  tubule.  It 
consists  of  two  walls,  an  outer  one  covered  with 
flattened  epithelium  resting  on  a  very  thin  basement 
membrane,  and  an  inner  wall  consisting  of  flattened 
epithelium  which  is  reflected  over  and  encloses  the 
glomerulus.  Thus  the  blood  in  the  capillaries  is 
separated  from  the  interior  of  Bowman's  capsule 
by  the  intervention  of  the  capillary  wall  and  the 
inner  layer  of  epithelium,  lining  the  inner  wall  of  the 
capsule.      The    secretion    of    urine    primarily    takes 


320  THE  URINARY  APPARATUS 

place  by  a  rise  of  blood  pressure  in  the  arterioles 
(afferent  vessels).  The  capsule  of  Bowman  becomes 
so  distended  that  the  two  layers  of  cells  approximate 
and  practically  obliterate  the  cavity  between  them. 
Then  the  water,  salts,  sugars,  peptones,  etc.,  pass 
from  the  blood  to  the  interior  of  the  capsule  of  Bow- 
man, by  a  process  of  filtration  or  transudation  through 
the  capillary  wall  and  the  thin  inner  layer  of  Bow- 
man's capsule,  and  pass  along  the  tubules.  However, 
Heidenhain  believes  that  the  latter  constituents  of 
the  urine  are  passed  through  the  glomerular  epithe- 
lium by  the  processes  of  cell  selection  and  cell  activity; 
in  other  words,  the  entire  constituents  of  the  urine 
obtained  in  the  capsule  of  Bowman  from  the  blood 
is  due  to  process  of  secretion,  assisted  or  regulated  by 
the  degrees  of  blood-pressure,  blood-velocity,  etc. 

The  blood  of  the  glomerulus  being  emptied  of  a 
portion  of  its  water,  salts,  etc.,  as  described  above, 
still  possesses  other  waste  products  in  the  blood 
which  must  be  eliminated  as  urea,  uric  acid,  etc.  This 
further  elimination  is  based  on  a  distinct  and  proved 
function  of  the  cells,  lining  the  convoluted  tubules  of 
the  kidney,  of  selecting  from  the  blood  and  secreting 
the  above-mentioned  products  as  constituents  of  the 
urine.  The  methods  by  which  these  products  leave 
the  glomerulus  and  reach  the  cells  of  the  convoluted 
tubules  is  as  follows :  A  small  arteriole  leaves  each 
glomerulus  (efferent  vessel)  and  divides  and  sub- 
divides, forming  a  capillary  net-work,  which  surrounds 
the  convoluted  tubules,  thus  bringing  the  blood  in 
intimate  relation  with  the  lining  cells  of  the  tubules, 
which,  to  repeat,  select  and  secrete  the  urea,  uric 
acid,  etc.,  from  the  blood,  and  eliminate  them  in  the 
urine. 

The  remaining  quantity  of  blood  which  has  given 
off  its  waste  product  to  be  eliminated  by  the  two 
methods  described  above,  is  taken  up  by  venules 
which  anastomose  with  the  arterioles  around  the  con- 


THE  URINARY  ORGANS  321 

voluted  tubules  and  straight  tubules,  and  is  returned 
through  the  renal  vein  to  the  venous  system. 

The  Urine. — The  urine  is  the  fluid  by  which  the 
end-products  resulting  from  tissue  metabolism  are 
excreted  or,  literally  speaking,  are  secreted  by  the 
kidneys  from  the  body.  The  phenomena,  however,  is 
essentially  the  same  as  takes  place  during  secretion  of 
fluids  by  the  body  cells.  It  must  be  remembered  that 
to  perform  work,  create  energy,  nourish,  and  develop 
the  body  from  birth  to  death,  food  is  necessary.  The 
body  receives  its  nourishment  from  the  food  we  eat,  and 
the  essential  constituents  of  the  same  are  used  by  the 
tissues  to  perform  the  various  and  complex  processes 
necessary  to  carry  on  and  maintain  the  normal  physio- 
logical functions  of  the  human  body.  Were  this 
intake  of  food  not  used  or  eliminated,  there  would 
be  a  general  interference  of  the  normal  functions  of 
cell  life,  but  as  we  have  demonstrated  in  previous 
chapters,  it  is  used  and  then  undergoes  changes,  the 
residue  forming  products  which  must  be  eliminated, 
and  the  urine  is  the  fluid  by  means  of  which  this 
occurs. 

Normal  urine  is  a  pale  yellow  or  amber-colored 
fluid,  with  an  aromatic  odor  and  acid  reaction.  Its 
specific  gravity  is  1.020,  but  varies  between  1.015  to 
1.025.  It  is  usually  transparent,  except  when  mucus, 
phosphates,  urates,  render  it  cloudy  in  appearance. 

The  color  varies  from  a  pale  yellow  to  a  reddish 
brown,  dependent  upon  the  physiologic  processes 
occurring  prior  to  elimination.  Its  color  is  due  to 
the  presence  of  a  pigment-urobilin,  urochrome,  uro- 
erythrin,  derived  from  the  bile  pigments  absorbed 
from  the  liver  or  alimentary  canal.  The  acidity  of 
the  urine  is  due  to  the  presence  of  acid  phosphates 
of  sodium  and  calcium.  Urine  is  usually  acid  in  the 
morning,  alkaline  or  neutral  following  digestion. 

The  quantity  of  urine  passed  in  twenty-four  hours 
amounts  to  40  to  50  ounces  (2|  to  3  pints  2  ounces). 
21 


322       THE  URINARY  APPARATUS 

The  odor  is  due  to  the  presence  of  aromatic  com- 
pounds. 

Composition  of  Urine: 

Water 1500.00  c.c. 

Total  solids 72.00  gm. 

Urea 33.18  gm. 

Uric  acid  (urates) 0.55  gm. 

Hippuric  acid  (hippurates) 0.45  gm 

Kreatinin,  xanthin,  hypoxanthin,  guanin, 

ammonium  salts,  pigments,  etc.        .      .  11.21  gm. 

Inorganic  salts,  sodium  and  potassium  sul-  "^ 
phates,  phosphates,  and  chlorides;  mag- 
nesium and  calcium  phosphates.       .      .>    27.00  gm. 

Organic  salts:  lactates,  acetates,  formates 
in  small  amounts  J 

Sugar a  trace. 

Gases — nitrogen  and  carbonic  acid. 

Urea,  being  the  most  abundant  and  important 
organic  compound  of  the  urine,  will  be  described. 
It  is  present  to  the  amount  of  2  to  3  per  cent.  It  is 
found  after  analysis  of  the  urine  to  consist  of  a 
colorless,  neutral  substance,  crystallizing  in  long, 
silky  needles.  It  is  composed  of  carbon,  oxygen, 
nitrogen,  and  hydrogen  (CON2H4).  The  daily  quantity 
excreted  amounts  to  30  to-  34  grams.  It  is  the  end- 
product  of  the  protein  metabolism  which  has  gone  on 
within  the  body,  and  the  quantity  excreted  in  the 
urine  is  dependent  upon  the  amount  of  protein  food 
consumed  and  upon  the  degree  to  which  the  protein 
constituents  of  the  tissues  have  undergone  metabolic 
changes. 

THE   SKIN 

The  skin  is  the  structure  investing  the  entire  outer 
surface  of  the  body,  blending  with  the  mucous  mem- 
branes which  bound  the  cavities  leading  into  the 
body,  as  the  mouth,  etc.  Its  dimensions  vary  in 
thickness  in  different  parts  of  the  body,  from  ^  to  y^ 


THE  SKIN  323 

of  an  inch,  total  area  16  to  20  square  feet  in  man,  and 
12  to  16  square  feet  in  woman. 

The  skin  secretes  a  clear,  colorless  fluid,  the  sweat; 
it  acts  as  a  protection  to  the  underlying  structures,  and 
aids  in  the  excretion  of  waste-products  of  metabolism, 
possessing  an  accessory  function  in  conjunction  with 
the  lungs  and  kidneys  of  elimination  of  these  products 
from  the  body.  It  also  assists  in  regulating  the 
temperature  of  the  body  by  promoting  heat  dissi- 
pation. 

The  skin  must  be  studied  under  the  microscope  in 
order  to  properly  grasp  its  structure.  There  are  two 
principal  layers,  superficial  and  deep;  the  former  is 
termed  the  epidermis,  the  latter  the  derma  or  corium. 

The  Epidermis. — This  consists  of  epithelial  cells 
derived  from  the  ectoderm.  There  are  two  layers 
within  the  epidermis:  superficial  or  horny  layer,  and 
deep  or  Malpighian  layer.  The  horny  layer  consists 
of  non-nucleated  scaly  cells  composed  of  keratin. 
The  surface  cells  of  this  layer  are  being  continually 
rubbed  off,  and  are  replaced  by  cells  from  the  Mal- 
pighian layer  underneath,  which  undergo  a  change 
and  are  converted  into  keratin  as  they  approach  the 
surface.  The  Malpighian  or  deep  layer  is  divided  into 
four  layers,  named  from  without  inward — stratum 
lucidum,  stratum  granulosum,  stratum  mucosum,  and 
the  stratum  germinativum.  The  stratum  mucosum 
contains  the  prickle  cells  which  contain  the  pigment 
granules  that  give  to  the  skin  its  different  individual 
and  racial  characteristics  in  regard  to  color. 

The  Derma,  Corium,  or  True  Skin. — This  is  com- 
posed of  the  two  layers:  superficial  or  papillary  layer, 
and  the  reticular. 

The  superficial  or  papillary  layer  lies  beneath  the 
epidermis.  It  contains  numerous  projections  called 
papillae,  arid  i^  composed  of  a  net-work  of  fine  bundles 
of  fibrous  tissue.    The  papillae  are  composed  of  fibrous 


324 


THE  URINARY  APPARATUS 


and  elastic  tissue.  They  project  from  the  true  skin 
or  corium,  and  enter  into  depressions  of  the  epidermis. 
The  reticular  layer  connects  the  skin  with  the  under- 
lying structures.  It  also  supports  the  minute  blood- 
vessels, lymphatics,  and  nerves  which  are  distributed 
to  the  papillae. 

The  subcutaneous  tissue  is  the  layer  beneath  the 
reticular  layer  of  the  true  skin,  which  holds  the  skin 
to  the  parts  beneath.    It  is  made  up  of  thin  connec- 

FiG.  116 


II8-| 


TOUCH  CORPUSCLE^^ 

STRATUM  CORNEUM  f 
STRATUM   LUCIDUMi  '" 
RETE  MUCOSUM  I  . —  'i 

TRATUM    PAPILLAReT' 
RATUM    RETICULARE  (  — 


SUBCUTANEOUS 
AREOLAR   TISSUE 


RIDGES  OF  SKIN 


ORIFK 
SUDOI 
DUCT 
SUDOI 


BODY 

S*^'-'-;^.  iT-J^SU  DO  F 

^'  GLANC 


Vertical  section  through  the  skin  of  the  finger  tip.  The  layers  of  the  epi- 
dermis and  of  the  corium.  The  subcutaneous  areolar  tissue.  The  sudoriferous 
or  sweat  gland.     (Toldt.) 


tive  tissue  which  crosses  repeatedly  and  forms  spaces. 
The  skin  in  certain  parts  is  held  firmly  to  the  under- 
lying structures  by  the  subcutaneous  tissue,  as  the 
skin  over  the  palms  and  soles  of  the  feet;  in  others 
it  is  loosely  attached  and  is  freely  movable,  as  the 
skin  over  the  front  of  the  arms  and  neck. 
The   skin   is   supplied   by   branches   of   the   larger 


THE  SKIN  325 

arteries  coursing  through  the  subcutaneous  tissues. 
These  form  minute  capillary  plexuses  which  send  off 
branches  to  form  other  plexuses  in  the  corium  and 
papillary  layer;  from  the  latter  branches  pass  to  the 
papilla,  sweat  glands,  sebaceous  glands,  fat,  and  hair 
follicles. 

The  Appendages  of  the  Skin. — They  are  the  nails, 
hairs,  the  sudoriferous  or  sweat  glands,  and  sebaceous 
glands. 

The  Nails. — ^These  are  flattened,  elastic  structures 
of  a  horny  texture,  placed  upon  the  back  surface  of 
each  distal  extremity  of  each  finger  and  toe.  The 
nail  is  implanted  by  means  of  a  portion  called  the 
root,  within  a  groove  in  the  skin.  The  rest  of  the  con- 
vex surface  of  the  nail  is  called  the  body.  Beneath  the 
root  and  body  is  a  portion  of  the  cutis  called  the 
matrix.  This  is  the  part  from  which  the  nail  grows. 
The  white,  crescentic-shaped  area  of  the  nail  seen 
behind  the  matrix  and  above  the  root  is  called  the 
lunula.  Its  color  is  due  to  its  being  less  vascular 
compared  to  the  remaining  portion  of  the  nail.  The 
nail  can  be  injured,  and  if  any  cells  of  the  Malpighian 
layer  remain,  a  new  nail  will  develop  from  these 
cells. 

The  Hairs. — They  are  found  in  certain  regions  of 
the  body.  They  act  as  a  protection  to  the  part;  pre- 
vent friction;  prevent  foreign  bodies  from  entering  the 
organs  they  protect,  as  the  eyes,  nose,  etc.  We  speak 
of  hairs  of  the  head,  of  the  eyebrows,  of  the  axilla,  of 
the  eyelids,  of  the  nose,  of  the  pubes,  and  of  the  skin. 
They  vary  much  in  length,  thickness,  and  quality. 
In  some  individuals  the  hair  is  straight,  in  others 
curly.  Hairs  usually  are  oblique  to  the  surface  from 
which  they  arise. 

Hairs  are  modifications  of  the  skin  (epidermis)  and 
consist  essentially  of  the  same  structure  as  it.  Hair 
consists  of  the  root,  the  part  implanted  in  the  skin; 


326  THE  URINARY  APPARATUS 

the  shaft,  the  portion  extending  from  the  surface;  and 
the  point. 

The  root  of  the  hair  presents  at  its  deep  extremity  a 
bulb-Uke  enlargement,  the  hair-bulb,  which  is  lodged  in 
a  follicular  involution  of  the  epidermis  called  the  hair 
follicle.  The  hair  follicle  commences  in  the  surface 
of  the  skin  with  a  funnel-shaped  opening,  and  passes 
inward  in  an  oblique  direction,  to  become  dilated  at 
its  deep  extremity  or  fundus,  where  it  corresponds 
with  the  bulbous  shape  of  the  hair  which  it  contains. 
Each  hair  follicle  has  at  its  base  a  small,  conical, 
vascular  eminence  or  papilla,  the  hair  papilla,  similar 
to  the  papillse  found  upon  the  surface  of  the  skin. 
The  latter  are  highly  vascular  and  probably  supplied 
with  nerve  fibrils.  Each  hair  follicle  has  an  opening  into 
it  near  its  free  extremity,  the  openings  or  orifices  of 
the  ducts  of  one  or  more  sebaceous  glands.  Connected 
with  the  hair  follicles  are  minute  bundles  of  involuntary 
muscle  fibers  called  arrectores  pilorum.  They  originate, 
from  the  superficial  surface  of  the  true  skin,  or  corium, 
and  are  inserted  into  the  outer  surface  of  the  hair 
follicle,  below  the  orifice  of  the  duct  of  the  sebaceous 
gland.  They  are  located  on  the  side  toward  which 
the  hair  slopes,  and  when  they  contract  elevate  the 
hair. 

The  Sebaceous  Glands. — These  are  simple  and  com- 
pound racemose  glands  which  open  into  the  hair 
follicle,  and  sometimes  the  skin  surface,  by  means  of 
a  duct.  These  glands  are  lodged  in  the  surface  of  the 
true  skin  or  corium.  They  are  very  plentiful,  and 
are  found  in  all  parts  of  the  body,  especially  in  the 
skin  of  the  face  and  scalp;  also  numerous  around  the 
openings  of  the  mouth,  anus,  nose,  and  external  ear, 
but  are  not  found  in  the  skin  covering  the  palms  of 
the  hands  and  the  soles  of  the  feet.  Their  structure 
consists  of  a  delicate  transparent  membrane,  enclosing 
epithelial  cells. 


THE  SKIN  327 

Sebum  is  the  oily  fluid  secreted  by  the  sebaceous 
glands.  It  contains,  by  analysis,  water,  epithelium, 
proteins,  fats,  cholesterin,  and  inorganic  salts. 

The  pouring-out  of  sebum  by  the  glands  is  not  a 
true  secretion,  but  occurs  as  a  result  of  multiplication 
and  breaking  down  of  the  gland  epithelium.  Sebum 
when  first  secreted  is  oily  and  semiliquid,  but  soon 
becomes  hard  and  acquires  a  cheese-like  consistency. 
It  lubricates  the  hair  and  skin  and  prevents  dryness 
and  roughness. 

Vemix  caseosa  is  the  whitish,  oily  substance  seen 
covering  the  body  of  the  newborn  child.  It  is  supposed 
to  keep  the  skin  in  a  normal  condition  by  protecting 
it  from  the  effects  of  the  long-continued  action  of  the 
amniotic  fluid  in  which  the  fetus  is  suspended  during 
intra-uterine  development. 

The  Sweat  Glands. — The  sweat  glands  are  the  glands 
which  when  active  promote  perspiration  and  aid  in 
heat  dissipation,  at  the  same  time  eliminating  waste 
products  as  the  result  of  body  metabolism,  brought  to 
them  by  the  blood. 

They  are  situated  in  the  lower  part  of  the  corium, 
derma,  or  true  skin,  and  sometimes  in  the  subcutaneous 
tissue.  The  glands  are  tubular,  and  the  lower  or 
inner  extremity  is  coiled  upon  itself  a  number  of 
times,  forming  a  rounded  mass.  Extending  from 
this  coil  to  the  epidermis  is  the  duct  which  follows 
a  straight  course  in  this  situation,  and  after  a  few 
spiral  turns,  opens  onto  the  surface  of  the  skin.  The 
glands  consist  of  epithelial  cells  which  rest  upon  a 
very  thin  basement  membrane.  These  glands  are 
very  numerous;  it  has  been  estimated  that  they 
average  from  2,000,000  to  2,500,000.  They  are  more 
abundant  in  some  localities  than  others.  Each  sweat 
gland  is  richly  supplied  with  bloodvessels  and  nerves 
(vasomotor  and  secretor). 

Perspiration. — Perspiration  or  sweat  is  the  fluid 
secreted  by  the  sweat  glands  of  the  skin.     It  is  a 


328  THE  URINARY  APPARATUS 

clear,  colorless  liquid  of  a  specific  gravity  varying 
from  1.003  to  1.006;  slightly  acid  in  reaction  and  salty 
to  the  taste.  Except  when  collected  from  the  soles 
of  the  feet  and  palms  of  the  hands,  it  is  mixed  with 
epithelial  cells  and  sebum — secreted  by  the  sebaceous 
glands.  The  amount  of  sweat  secreted  in  twenty-four 
hours  has  been  estimated  at  700  to  1000  grams;  however, 
this  is  uncertain,  owing  to  the  difficulty  of  collection, 
and  the  influence  temperature,  diet,  drink,  season  of 
the  year,  etc.,  exert  upon  its  secretion. 

The  secretion  of  sweat,  though  essentially  an  ex- 
cretion, is  chiefly  concerned  in  the  regulation  of  the 
body  temperature  in  maintaining  heat  dissipation, 
rather  than  the  elimination  of  waste  materials  by 
means  of  the  sweat  glands  brought  to  them  by  the 
blood  and  lymph  vessels. 

The  Part  Played  hy  the  Nerve  System  on  the  Produc- 
tion of  Sweat. — The  secretion  of  sweat  is  practically 
the  result  of  the  activity  of  the  epithelial  cells  of  the 
sweat  glands  and  is  regulated  by  the  nerve  system. 
The  fluid  contained  in  the  sweat  is  derived  from 
the  materials  in  the  lymph  channels,  furnished  by 
the  blood. 

To  produce  sweat  there  must  be  a  glandular  activity, 
and  a  regulation  of  the  blood-supply.  The  former  is 
brought  about  by  a  set  of  nerves  called  the  secretor, 
which  stimulate  the  cells  to  activity;  the  latter  is 
regulated  by  nerves  called  the  vasomotor,  that  regu- 
late the  blood-pressure  of  the  capillaries  and  increase 
or  decrease  the  blood-supply  to  the  glands.  Other 
influences  increase  the  production  of  sweat,  by  their 
related  nerve  centres  sending  out  impulses  in  two 
ways:  first,  by  nerve  impulses  from  the  central  domin- 
ating centre,  supposed  to  be  located  in  the  medulla, 
being  stimulated  by  mental  emotions,  as  shock,  shame, 
etc.,  venosity  of  the  blood,  hot  drinks,  violent  muscular 
exercise,  etc.;  second,  by  reflex  impulses  being  con- 
veyed to  the  centres  in  the  spinal  cord  by  the  sensor 


QUESTIONS  329 

nerves  in  the  skin,  as  a  result  of  hot  applications,  high 
external  temperature,  etc. 

The  nerve  centres  which  regulate  the  secretion  of 
sweat  are  located  in  the  spinal  cord  and  reach  the 
glands  of  the  skin  by  means  of  the  sympathetic  nerves 
with  which  the  spinal  nerves  communicate.  The  domi- 
nating centre  which  is  influenced  to  activity  by  emotional 
states,  etc.,  is  situated  in  the  medulla  oblongata 
and  sends  its  impulses  down  the  spinal  cord  and  out 
through  the  spinal  nerves  and  the  sympathetic  system 
to  the  cells  of  the  glands.  Sweat  may  be  produced 
by  a  general  relaxation  of  the  bloodvessels  which 
supply  the  sweat  glands,  resulting  from  a  stimulation 
of  the  vasomotor  nerves.  But  it  must  be  remembered 
that  a  normal  production  of  sweat  is  based  on  the 
activity  of  both  the  nerves  influencing  the  blood 
supply  to  the  glands,  and  the  nerves  which  stimulate 
the  cells  of  the  sweat  glands  to  secrete. 


QUESTIONS 

1.  What  organs  include  the  urinary  apparatus? 

2.  Give  the  location  of  the  kidneys. 

3.  Which  is  higher,  the  right  or  left? 

4.  Give  dimensions  and  weight. 

5.  Are  the  kidneys  behind  the  peritoneum? 

6.  How  are  the  kidneys  held  in  position? 

7.  What  do  you  understand  by  the  medulla  and  cortex  of  the 
kidney  substance? 

8.  How  many  pyramids  are  there  in  the  medulla? 

9.  What  part  of  the  pyramids  drain  the  urine  into  the  pelvis  of 
the  ureter? 

10.  What  structures  form  the  medullary  rays  in  the  cortex  of 
the  kidney?    The  labyrinth? 

11.  What  structures  form  Bowman's  capsule?    The  glomerulus? 

12.  What  structures  form  the  renal  or  Malpighian  corpuscles  in 
the  cortex? 

13.  Where  do  the  uriniferous  tubules  commence  in  the  substance 
of  the  kidney?    Where  do  they  terminate? 

14.  What    type    of    epithelium    lines    Bowman's    capsule?      The 
convoluted  portion  of  the  uriniferous  tubules?    The  loops  of  Henle? 

15.  How  many  ureters  are  there? 

16.  What  is  the  function  of  the  ureters?    How  long  is  each  one? 

17.  Give  the  location,  dimensions,  and  capacity  of  the  bladder. 


330  THE  URINARY  APPARATUS 

18.  Name  the  portions  of  the  bladder. 

19.  Through  what  structure  does  the  urine  leave  the  bladder? 

20.  Describe  how  the  waste  products  of  the  blood  pass  through 
the  capsule  of  Bowman  during  urine  secretion. 

21.  What  function  do  the  cells  of  the  uriniferous  tubules  play  as 
regards  the  elimination  of  urea,  uric  acid,  etc.,  from  the  blood- 
stream? 

22.  How  does  the  venous  blood  from  the  capillaries  of  the  kidney 
reach  the  venous  system? 

23.  What  resulting  products  of  metabolism  does  the  urine  repre- 
sent? 

24.  How  much  urine  should  be  passed  daily  by  a  healthy  indi- 
vidual? 

25.  What  is  the  normal  color  of  urine? 

26.  What  end-product  does  urea  represent  in  the  urine? 

27.  Will  a  diet  rich  in  protein  increase  the  amount  of  urea? 

28.  What  are  the  functions  of  the  skin? 

29.  Name  the  two  principal  layers  of  the  skin. 

30.  What  is  the  function  of  the  subcutaneous  tissue? 

31.  Name  the  appendages  of  the  skin. 

32.  Name  the  parts  of  a  nail. 

33.  Name  the  functions  of  hairs. 

34.  Name  the  parts  of  a  hair. 

35.  Describe  a  hair  follicle. 

36.  What  muscles  cause  hairs  to  stand  erect? 

37.  Which  layer  of  the  skin  lodges  the  sebaceous  glands?  When 
do  they  empty?  In  what  portions  of  the  body  are  they  most  abun- 
dant?   Absent? 

38.  What  is  the  secretion  from  the  sebaceous  glands  called?  Its 
function? 

39.  Describe  vernix  caseosa. 

40.  In  which  layer  of  the  skin  are  the  sweat  glands  located? 

41.  Do  they  possess  ducts,  and  when  do  they  pour  out  their 
secretion? 

42.  What  are  the  functions  of  the  sweat  glands? 

43.  Is  sweat  acid  or  alk.aline  in  reaction? 

44.  Does  the  secretion  of  sweat  aid  heat  dissipation? 

45.  Name  the  nerves  which  stimulate  the.  cells  of  the  sweat  glands 
to  secrete,  also  regulate  the  blood-supply  to  a  sweat  gland. 


CHAPTER  XVII 

ANATOMY  AND  PHYSIOLOGY  OF  THE 
NERVE  SYSTEM 

The  nerve  system  is  divided  for  the  purpose  of 
description  into  the  cerebrospinal  and  sympathetic 
systems.  The  cerebrospinal  system  consists  of  the 
central  nerve  axis  (brain  and  spinal  cord),  and  the 
peripheral  nerves  (cranial  and  spinal). 


THE    STRUCTURE    OF   THE   NERVE    SYSTEM 

Neurone,  or  Nerve  Cell  Element.  ^ — The  essential 
structure  from  which  all  the  functions  of  the  human 
body  arise  as  a  result  of  innervation,  is  the  cell  ele- 
ment called  the  neurone.  They  differ  from  all  the 
other  cells  in  the  tissues,  in  that  their  protoplasm 
is  extended  in  the  form  of  processes,  and  these 
reach  some  distances  from  the  nuclear  portion  of  the 
cell.  , 

The  neurones  are  the  essential  structures  concerned 
in  all  nerve  reflex.  However,  the  fact  of  a  sensor 
impulse  reaching  a  neurone  from  a  muscle,  gland,  or 
other  cell,  does  not  say  a  motor  impulse  will  be  returned 
from  the  neurone  direct,  as  the  neurones  are  connected 
with  other  neurones  by  means  of  their  extending 
processes,  which  have  the  power  of  reacting  and 
sending  out  excitomotor  impulses,  and  of  checking 
or  reducing  the  impulse  to  the  structure  to  be  inner- 
vated. 


332 


THE  NERVE  SYSTEM 


The  neurones  form  an  aggregation  of  cells  which 
are  the  basis  of  the  nerve  system  from  which  all 


Showing  some  varieties  of  ceil  bodies  of  neurones  (diagrammatic).  A. 
Unipolar  (amacrine)  cell  from  the  retina.  B.  Bipolar  cell  from  vestibular 
ganglion.  C.  Multipolar  cell,  with  long  axone,  from  spinal  cord.  D.  "Golgi 
cell,"  with  short  axone  breaking  up  into  numerous  temiinal  twigs.  E.  Pyrami- 
dal cell  from  cerebral  cortex,    a.  Axone.     cU.  Collaterals,     t.  Telodendria. 


THE  STRUCTURE  OF  THE  NERVE  SYSTEM     333 

nerve  force  originates,  and  which  maintains  the 
specific  functions  of  the  body  expressed  in  motion, 
trophic  changes,  or  stimuli  of  a  chemic,  mechanic 
(touch,  sound),  thermal,  or  photic  nature. 

Neurones  are  so  arranged  to  be  receptive  and 
receive  (afferent)  impulses  from  other  parts  of  the 
body.  These  are  termed  sensor  neurones.  Others 
are  emissive  and  return  (efferent)  impulses;  the  latter 
are  called  motor  neurones;  if  connected  with  muscle 
cells,  excitomotor,  and  with  gland  cells,  excito- 
glandular. 

The  neurones  or  nerve  cells  compose  the  cellular 
element  of  the  whole  nerve  system,  and  the  balance 
is  the  supporting  white  fibrous  tissue  and  neuroglia 
derived  from  the  supporting  membrane  or  from  the 
sheaths  of  vessels. 

The  Structure  of  a  Neurone  or  Nerve  Cell. — It  consists 
of  a  cell  mass  or  body  containing  a  nucleus,  and  within 
the  latter  a  nucleolus.  From  this  cell  body  are  given 
off  protoplasmic  processes  of  two  different  varieties: 
(1)  dendrites,  and  (2)  axone,  or  axis-cylinder. 

The  Bodies  of  Nerve  Cells. — They  vary  in  size, 
they  measure  4  to  135  microns  or  more  in  diameter, 
and  when  it  is  considered  that  1  micron  is  equal  to 
Yo^TUo"  of  an  inch,  their  minute  size  may  be  appreciated. 
Neurones  are  classified  according  to  the  number  of 
processes  arising  from  the  body,  as  unipolar,  bipolar, 
and  multipolar. 

The  Dendrites.  —  They  are  processes  extending 
from  the  body  of  the  cell  in  large  numbers.  They 
consist  of  the  same  structure  as  the  cell,  and  thus 
increase  the  functional  surface  or  expression  of  the 
cell.  The  dendrites  never  communicate  with  the 
branches  of  the  same  process  direct,  or  anastomose 
with  the  terminals  of  dendrites  from  adjoining  nerve 
cells.  The  function  of  the  dendrites  is  supposed  to 
be    conductive    and    receptive    for    nerve    impulses. 


334  THE  NERVE  SYSTEM 

Small  buds  are  seen  at  times  along  the  course  of 
dendrites.     They  are  called  gemmules. 

Axone,  or  Axis-cylinder.  —  This  arises  from  the 
body  of  the  neurone,  or  nerve  cell,  as  a  cone-shaped 
process,  and  is  seen  as  a  very  delicate  fiber.  In 
structure  it  differs  from  the  dendrites.  Each  axone 
is  uniform  in  diameter;  and  consists  of  fine  fibrillse, 
embedded  in  a  clear  protoplasmic  substance  (neuro- 
plasm). Axones  may  be  very  short  or  as  much 
as  a  meter  in  length.  As  a  rule,  only  one  axone 
is  given  off  from  a  cell,  and  this  form  is  termed  mon- 
axic  neurones ;  however,  more  than  one  is  present;  as 
two  axones,  they  are  termed  diaxonic  neurones;  and 
several  axones,  polyaxonic  neurones. 

Axones  in  certain  portions  of  the  nerve  system 
(brain  and  spinal  cord)  possess  fine  branches  called 
collaterals;  they  have  the  same  structure  as  the  axone 
from  which  they  arise.  Some  axones,  as  Golgi  cells, 
break  up  into  branches  after  leaving  the  cell  body, 
called  dendraxones.  The  minute  endings  of  the  axis- 
cylinders  and  collaterals,  which  spread  out  like  the 
branches  of  a  tree,  are  termed  telodendria. 

The  axone  is  the  functional  element  of  the  nerve 
system  which  acts  as  the  distributive  or  emissive 
conductor  of  nerve  impulses. 

Nerve  Fibers. — Nerve  fibers  are  simply  continua- 
tions of  the  axis-cylinder  or  axone  given  off  from  the 
cell  body  of  a  neurone,  with  their  surrounding  invest- 
ments, the  myelin  and  neurilemma.  They  are  classi- 
fied into  two  varieties,  according  to  whether  or  not 
the  axis-cylinder  possesses  a  medullary  or  myelin 
sheath,  viz.,  medullated  or  myelinic  nerve  fibers  and 
non-medullated  or  amyelinic  nerve  fibers. 

Medullated  Nerve-fibers. — These  possess  three  distinct 
minute  anatomical  portions,  when  subjected  to  stain- 
ing methods  and  examined  under  the  microscope, 
namely:  An  external  investing  sheath,  the  neurilemma; 


THE  STRUCTURE  OF  THE  NERVE  SYSTEM     335 

an  intervening  semifluid  substance,  the  medulla  or 
myelin;  and  an  internal  dark  thread,  the  axis-cylinder 
or  axone. 

The  neurilemma  is  a  delicate,  transparent  membrane 
investing  the  myelin  and  axone,  and  occurs  wherever 
the  meylin  sheath  is  absent.  It  possesses  a  nucleus, 
which  may  be  seen  between  the  nodes  of  Ranvier  along 
the  course  of  the  nerve.  It  acts  as  a  protective  mem- 
brane to  the  nerve-fiber.* 

The  medulla,  myelin,  or  white  substance  of  Schwann 
lies  between  the  neurilemma  and  invests  the  axone. 
This  is  the  substance  of  the  nerve  fiber,  the  presence 
of  which  imparts  to  the  nerve  tissue  its  white  appear- 
ance, and  gives  rise  to  the  term  white  fibers  in  speaking 
of  nerve  tissue,  to  differentiate  them  from  gray  fibers, 
the  latter  having  no  myelin  sheath. 

Along  the  course  of  nerve  fibers  may  be  seen  a 
diminution  or  shrinkage  in  its  caliber,  due  to  an 
absence  of  the  myelin  Aeath,  permitting  the  neuri- 
lemma to  be  in  direct  ^position  to  the  axis-cylinder, 
^hese  narrowed  parts  are  called  the  nodes  of  Ranvier, 
named  after  their  discoverer.  The  portion  of  the 
nerve  fiber  between  these  interruptions  is  termed  the 
intemodal  segment.  Axones  give  off  their  collateral 
branches  at  the  nodes  of  Ranvier. 

Non-medullated  or  Amyelinic  Nerve  Fibers. ^ — These  are 
devoid  of  a  myelin  ^ath,  or  the  white  substance  of 
Schwann,  thus  prjpenting  a  gray  appearance,  and 
giving  origin  to  f^ie  term  gray  fibers.  Some  non- 
medullated  nerve  fibers  possess  only  an  axis-cylinder, 
or  axone.  These  are  found  in  the  central  ganglia. 
Others  possess  a  neurilemma  investing  the  single 
axis-cylinder,  and  are  the  main  variety  of  nerve  fiber 
constituting  the  sympathetic  system.  Non-medullated 
nerve  fibers  are  not  so  abundant  throughout  the 
nerve  system  as  the  medullated  variety. 

Nerves. — Nerves  are  round,  flattened  bundles  of 
axones,  held  firmly  together  by  investing  connective 


Fig.  118 


Scheme  of  central  motor  neurone.  (I  type  of  Golgi.)  The  motor  cell 
body,  together  with  all  its  protoplasmic  processes,  its  axis-cylinder  process, 
collaterals,  and  end  ramifications  represent  parts  of  a  single  cell  or  neurone, 
a.h.,  axone-hillock  devoid  of  Nissl  bodies  and  showing  fibrillation,  c,  cyto- 
plasm showing  Nissl  bodies  and  lighter  ground  substance.  to',  nucleolus. 
(Barker.) 


THE  STRUCTURE  OF  THE  NERVE  SYSTEM     337 

tissue.  The  latter  contains  the  bloodvessels  and 
lymphatics.  Nerves  are  the  connecting  trunks  which 
bring  the  brain  and  spinal  cord  in  relation  with  the 
structures  throughout  the  body — muscles,  skin,  glands, 
etc. 

Structure  of  Nerves. — Examined  under  the  micro- 
scope, each  nerve  shows  on  cross-section  a  collection 
of  nerve  fibers,  or  axones,  arranged  in  bundles.  The 
entire  group  being  invested  by  a  layer  of  connective 
tissue  called  the  epineurium;  however,  each  separate 
bundle  of  fibers  within  the  nerve  is  enclosed  in  its 
own  connective-tissue  sheath  —  the  perineurium,  and 
the  numbers  of  axis-cylinders,  or  axones,  within  the 
bundles  ar«  again  enclosed  in  a  delicate  connective- 
tissue  net-work  called  the  endoneurium,  or  sheath  of 
Henle. 

Nerves  as  they  pass  from  the  brain  or  spinal  cord 
are  surrounded  by  the  epineurium,  and  divide  and 
subdivide  as  they  give  off  branches  to  other  nerves,  and 
pass  to  their  terminations.  As  each  branch  is  given 
off  the  same  sheath  of  connective  tissue  that  enclosed 
the  parent  nerve  accompanies  it.  This  arrangement 
continues  as  the  branches  become  smaller  and  smaller, 
until  they  reach  their  terminal  point  of  distribution, 
where  only  a  single  nerve  fiber  remains,  enclosed  by  a 
transparent  membrane,  the  endoneurium  or  sheath 
of  Henle.  However,  near  the  ultimate  termination 
of  a  nerve  the  single  nerve  fiber  may  continue  to  give 
off  branches,  each  one  consisting  of  the  axis-cylinder 
and  myelin  sheath. 

The  multitude  of  nerve  cells  or  neurones  entering 
into  the  formation  of  the  nerve  system  are  supported 
in  a  non-neural  or  inactive  set  of  cells  as  regards  nerve 
activity,  called  the  supporting  tissue  elements  of  the 
nerve  system.  These  consist  of  two  kinds :  (1)  neuroglia, 
and  (2)  connective-tissue  trabecules  derived  from  the  pia 
mater,  or  the  bloodvessel  channels.  Neuroglia  consist 
22 


338 


THE  NERVE  SYSTEM 


Fig.    119 


Neuralgia  cells  of  brain  shown 
by  Golgi's  method.  A.  Cell  with 
branched  processes.  B.  Spider-cell 
with  unbranched  processes.  (After 
Andriezen.)  (From  Schiifer's  Essen- 
tials of  Histology.) 


of  cells— glia  cells  and  glia 
fibers.  There  are  two  varie- 
ties of  the  latter — ependy- 
mal  cells  and  astrocjrtes. 
The  supporting  tissue  ele- 
ments of  the  brain,  etc., 
do  not  possess  the  power 
of  developing  or  conveying 
nerve  impulses;  they  are 
spoken  of  as  non-neural. 

The  Origin  of  Nerves. 
— Efferent  nerves,  those 
which  conduct  impulses 
to  the  periphery,  muscles, 
glands,  bloodvessels,  etc., 
in  response'to  stimuli  from 
the  brain  and  spinal  cord, 
originate  in  the  nerve  cells 
of  the  gray  substance  of 
these  structures,  and  the 
axones  are  prolonged  to 
form  the  nerve  fibers. 
Nerves  emerge  from  the 
brain  and  spinal  cord  as 
single  rounded  cords.  They 
may  possess  only  a  single 
root  of  origin  or  two  roots 
widely  apart  from  each 
other,  yet  each  of  the  two 
roots  may  be  different  in 
function,  as  seen  in  the 
spinal  nerves,  the  anterior 
root  being  motor  or  effer- 
ent, the  posterior  sensor  or 
afferent.  The  point  at 
which  a  single  nerve  root 
leaves  the  brain  or  spinal 
cord  is  called  the  super- 
ficial   origin    of    a    nerve; 


THE  STRUCTURE  OF  THE  NERVE  SYSTEM     339 

however,  a  tracing  of  the  axones  of  these  nerves  for 
a  distance  into  the  gray  substance  of  the  brain  or 
spinal  cord,  where  they  originate,  will  end  in  the 
nerve  centre,  which  is  termed  the  deep  origin  of  a 
nerve. 

Endings  of  Nerves. — It  must  be  remembered  that 
the  course  or  appearance  of  a  nerve  has  nothing  to  do 
with  its  function,  for  from  all  external  or  microscopic 
examination  an  efferent  nerve  cannot  be  differenti- 
ated from  an  afferent  nerve."  Nerves  end  in  several 
ways,  which  vary  in  different  situations. 

The  Efferent  or  Centrifugal  Nerves.  —  This  variety 
is  motor  and  conveys  nerve  impulses  away  from  the 
brain  and  spinal  cord.  Upon  reaching  their  final 
ending,  these  lose  both  the  neurilemma  and  myelin 
sheath.  The  axis-cylinder  divides  and  gives  off 
branches  (collaterals)  which  join  with  other  axones. 
These  axis-cylinders  Come  in  direct  contact  with  the 
tissue  cells  and  are  termed  end  arborizations,  or 
telodendria,  also  end-organs,  terminal  organs,  or  end- 
tufts. 

In  muscles  of  the  skeleton  the  axones  of  the  nerves 
lose  their  neurilemma  and  myelin  sheath;  at  the 
point  they  join  the  muscle  fiber,  and  after  giving  off 
branches  within  the  sarcolemma,  appear  to  lie  in  a 
mass  of  sarcoplasm  and  nuclei  which  forms  the 
motor-plate. 

In  the  muscles  of  the  viscera  (involuntary)  the 
nerve  fibers  are  non-meduUated,  and  belong  to  the 
sympathetic  system  or  other  neurones.  The  axones 
divide  and  subdivide  to  form  plexuses  which  invest 
the  muscle-cell  bundles.  Other  branches  are  given 
off  from  the  latter  which  finally  come  in  intimate 
relation  with  each  cell,  upon  the  surface  of  which 
they  are  seen  as  granular  masses. 

In  the  glands  the  nerve  fibers  are  derived  from  the 
sympathetic   and   other   neurones;   the   axones   reach 


340  THE  NERVE  SYSTEM 

the  acini  of  the  glands,  upon  the  outer  surface  of 
the  acini;  they  form  plexuses  which  pierce  the  acini 
wall,  and  give  off  minute  branches  to  the  gland 
cells. 

The  Afferent  or  Centripetal  Nerves.  —  These  end 
as  the  former,  but  as  this  variety  of  nerve  is  sensor, 
and  conveys  sensations  to  the  brain  and  spinal  cord, 
the  end-tufts  are  in  intimate  relation  with  specialized 
end-organs,  which  are  essential  to  the  appreciation 
of  the  complex  sensations,  viz.,  of  sight,  the  retina 
in  the  eye;  taste,  the  taste-buds  in  the  tongue;  smell, 
the  olfactory  cells  in  the  nasal  mucous  membrane; 
hearing,  the  organ  of  Corti  in  the  ear. 

In  the  skin  and  mucous  membranes  the  axones 
are  in  intimate  contact  with  various  end-organs  which 
give  rise  to  the  numerous  conscious  sensations  of 
touch,  heat,  thirst,  hunger,  and  muscle  sense,  etc. 
The  following  are  the  chief  names  of  the  various 
end-organs : 

1.  Free  endings  in  the  skin. 

2.  Tactile  cells  of  Merkel. 

3.  Tactile  corpuscles  in  the  papilla  of  the  true  skin. 

4.  Tactile  corpuscles  of  Meissner. 

5.  Pacinian  corpuscles  found  attached  to  the  nerves 
of  the  hands,  feet,  intercostal  nerves,  and  nerves  in 
other  situations. 

6.  End-buds  of  Krause  in  the  conjunctiva,  clitoris 
(female),  penis  (male),  etc. 

The  Nerve  Plexus. — It  consists  of  a  number  of 
nerves  communicating  with  other  nerves,  by  means 
of  collateral  branches.  Some  plexuses  are  formed  by 
direct  branches  being  given  off  from  the  spinal  cord,  as 
the  brachial,  lumbar,  sacral  plexuses;  others  are  formed 
by  the  terminal  filaments  of  nerve  fibers,  as  the 
plexuses  in  the  skin,  etc.,  still  others  may  contain 
sympathetic  nerve  fibers  derived  from  the  sympathetic 
system,  in  addition  to  the  sensor  and  motor  nerves. 


THE  STRUCTURE  OF  THE  NERVE  SYSTEM     341 

Fig.  120 


Showing  some  varieties  of  peripheral  terminations  of  afferent  neurones 
(or  "peripheral  nerve  beginnings"):  A.  Terminal  fibrillae  in  epithelium  (after 
Retzius).  B.  Tactile  corpuscle  (Meissner's,  after  Dogiel).  C.  Bulboid 
corpuscle  (Krause's,  after  Dogiel).  D.  Lamellated  corpuscle  (Pacini's,  after 
Dogiel,  Sala,  and  others).  E.  Genital  nerve  corpuscle  from  human  glaus 
penis  (after  Dogiel).    a.  Axone.    t.  Telodendria 


342  THE  NERVE  SYSTEM 

In  other  words,  the  various  nerve  fibers,  in  forming 
a  plexus,  maintains  the  same  function  which  the 
nerve  possesses  from  its  origin,  as  motor,  sensor,  or 
sympathetic. 

Ganglia. — Aside  from  the  arrangement  of  neurones 
or  nerve  cells  in  the  cerebrospinal  system,  there  is 
another  collection  of  these  neurones  into  small  groups, 
connected  with  each  other  and  the  nerves  of  the 
brain  and  spinal  cord  called  ganglia.  Some  ganglia 
are  large  enough  to  be  seen  by  the  naked  eye,  others 
are  so  small  that  they  can  scarcely  be  detected,  unless 
examined  by  a  lens  or  microscope.  Ganglia  compose 
the  sympathetic  system.  They  contain  nerve  cells 
with  dendrites  and  axones,  the  greater  number  of 
the  latter  being  non-medullated,  and  are  surrounded 
by  a  connective-tissue  capsule. 

Ganglia  are  found  on  the  dorsal  or  posterior  root 
of  the  spinal  cord,  on  the  sensor  root  of  the  fifth  nerve, 
on  the  facial  and  auditory  nerves;  and  on  the  vagus 
and  glossopharyngeal,  along  either  side  of  the  spinal 
column,  where  they  form  the  gangliated  cord  of 
the  sympathetic.  Ganglia  are  receptive  to  impulses 
from  nerves  and  other  ganglia,  and  have  the  prop- 
erty of  conducting  impulses  to  other  ganglia  and 
nerves. 

Classification  of  Nerves. — Nerves  are  pathways  of 
communication  between  the  brain  and  spinal  cord, 
and  the  structures  throughout  the  body  which  are 
dependent  upon  the  nerve  system  for  their  develop- 
ment, growth,  repair,  and  actions,  and  they  require 
the  stimuli  from  the  brain  to  excite  into  physiologic 
activity  the  cells  of  muscles,  glands,  skin,  mucous 
membranes,  organs  of  the  thorax,  abdomen,  etc. 

There  are  two  sets  of  nerves  concerned  in  all  nerve 
action  or  reflex.  One  which  transmits  impulses  from 
the  brain  and  spinal  cord  to  the  structure  whose 
activities    are    to    be    increased    or    retarded;    others 


THE  STRUCTURE  OF  THE  NERVE  SYSTEM     343 

transmit  impulses  from  the  peripheral  surfaces  and 
organs  of  the  body  to  the  brain  and  spinal  cord,  which 
create  conscious  sensations  or  stimulate  other  reflex 
activity.  The  former  are  termed  efferent  or  centrifugal 
(mostly  motor  nerves),  the  latter  afferent  or  centripetal 
(mostly  sensor  nerves). 

Physiology  of  Nerves. — Nerves  possess  the  function 
of  developing  and  conducting  nerve  impulses  from 
the  nerve  centres  in  the  brain  and  spinal  cord  to  the 
periphery  of  the  body,  and  at  the  same  time  to  trans- 
mit nerve  impulses  from  the  periphery  to  the  centres 
in  the  brain  and  spinal  cord.  As  long  as  a  nerve 
is  capable  of  these  qualities  it  is  termed  excitable 
or  irritable,  or  possessed  with  irritability  or  excita- 
bility. 

Nerve  Stimuli. — Nerves  must  receive  some  form 
of  external  stimulation  before  they  will  develop  or 
convey  nerve  impulses,  as  they  do  not  possess  the 
property  of  spontaneously  developing  and  sending 
out  nerve  impulses.  A  stimulus  to  motor  nerves 
(efferent),  which  excite  it  to  activity,  arise  as  a  result 
of  some  molecular  disturbance  within  the  nerve  cells, 
that  acts  upon  the  nerve  fibers  in  connection  with 
them.  In  the  case  of  sensor  nerves  (afferent)  the 
stimulus  arises  in  the  end-organs,  which  convey  the 
nerve  impulse  to  the  sensor  nerve  fibers  in  connection 
with  them. 

Nerves  react  to  stimulation  according  to  their 
habitual  function  and  distribution.  If  we  stick  our 
finger  with  a  pin,  the  sensation  of  pain  is  felt,  due  to 
the  fact  that  a  sensor  nerve  has  conveyed  the  nerve 
impulse,  started  in  the  end-organs  in  the  skin,  to  the 
conscious  centres  in  the  brain;  stimulation  of  the  end- 
organs  in  rods  and  cones  in  the  retina  of  the  eye  give 
rise  to  the  sensation  of  light;  stimulation  of  a  motor 
nerve  is  followed  by  the  contraction  of  a  muscle 
which  it  innervates.     Nerve  function  is  supposed   to 


344  THE  NERVE  SYSTEM 

depend  upon  the  peculiarities  inherent  in  the  central 
and  peripheral  end-organs,  regardless  of  its  con- 
struction and  the  character  of  the  stimuli  (Brubaker's 
Physiology) . 

Special  Stimuli. — These  comprise  the  group  which 
act  upon  the  nerves  of  special  sense  and  give  rise  to 
conscious  sensations,  through  the  highly  specialized 
end-organs,  which  transfer  the  nerve  impulse  to  the 
filaments  of  the  nerves  in  relation  with  them. 

The  afferent  nerves  (sensor)  convey  the  impulse  to 
the  higher  conscious  centres,  in  response  to  the  special 
stimuli,  as  follows:  (1)  Light  or  etheral  vibra- 
tions act  upon  the  end-organs  of  the  optic  nerve 
in  the  retina  (sight  and  light);  (2)  sounds  act  upon 
the  end-organs  of  the  auditory  nerve  (hearing)  in  the 
ear;  heat  or  vibrations  of  the  air  act  upon  the  end- 
organs  in  the  skin;  (4)  chemic  agents  act  upon  the 
end-organs  of  the  olfactory  (smell)  and  gustatory 
(taste)  nerves  of  the  nose  and  tongue  respectively. 

The  efferent  nerves  (motor)  convey  impulses  to  the 
muscles,  glands,  etc.,  in  response  to  stimuli  which 
are  supposed  to  arise  as  a  result  of  a  molecular  dis- 
turbance in  the  central  nerve  cell,  a  combination  of 
physical  and  chemic  processes  attended  by  the  libera- 
tion  of  energy,  which  passes  from  molecule  to  molecule. 
The  passage  of  the  nerve  impulse  is  accompanied  by 
changes  of  electric  tension. 

Thus,  to  sum  up,  all  nerve  impulses  have  their 
origin  in  the  nerve  cells  or  neurones,  and  these  millions 
of  associated  neurones  are  the  basis  of  all  nerve  activity. 
A  theory  has  been  created  to  simplify  the  understand- 
ing of  nerve  cell  activity.  It  is  called  the  neurone  theory 
of  Waldeyer,  who  explains  it,  based  on  the  works  of 
Golgi,  Cajal,  Forel,  and  others,  as  follows:  (1)  Each 
neurone  is  a  distinct  and  separate  entity;  (2)  the 
collaterals  and  other  terminals  of  the  neurones  form 
no  connections  among  themselves;   (3)   neurones  are 


THE  CENTRAL  NERVE  SYSTEM 


345 


associated,  and  impulses  conveyed,  by  contact  or 
contiguity  of  the  axonic  terminals  of  one  axone  with 
the  cell  body  or  dendrites  of  another  neurone. 

THE   CENTRAL    NERVE    SYSTEM 

The  central  nerve  system  or  cerebrospinal  axis 
consists  of  the  (1)  brain  (encephalon)  and  its  cranial 
nerves  and  associated  ganglia;  (2)  the  spinal  cord  and 
its  spinal  nerves  and  associated  ganglia. 

Fig.  121 


ARTERIA 
VERTEBRALIS 


N.CEfrvTl 


LIGAMENTUM 
OENTICULATUM 


Ventral  view  of  medulla  oblongata  and  upper  part  of  spinal  cord.  Dura 
and  arachnoid  cut  along  median  line  and  folded  aside.  A  and  B  are  fairly 
constant  velar  folds  of  the  arachnoid.     (After  Key  and  Retzius.) 


The  Spinal  Cord. — The  spinal  cord  is  the  portion 
of  the  nerve  svstem  which  is  connected  with  the  brain 


346 


THE  NERVE  SYSTEM 


above  and  the  periphery  of  the  body  by  thirty-one 
pairs  of  nerves.  It  is  lodged  in  the  spinal  canal, 
ensheathed  by  the  membranes,  dura  mater,  arachnoid, 
and    pia  mater,   and  commences  above  at  the  atlas 


Fig.  122 


SULCO-MARGINAL   TRACT     VENTRAL    VESTIBULOSPINAL   TRACT 
FROM  SUP.  QUADRIG.  FROM    FASTIGIUM    (LuWCnthal's) 


Fig.   123 


SIXTH 
THORACIC 


VENTRAL   VtSTIBULOSPINAL   TRACT 


THE  CENTRAL  NERVE  SYSTEM 


347 


Fig.  124 


WHITE    VENTRAL    COMMISSURE 

Figs.  122,  123,  and  124. — Sections  of  the  spinal  cord  at  the  level  of  the 
sixth  cervical,  sixth  thoracic,  and  third  lumbar  segments,  the  conducting 
tracts  being  indicated  on  the  right  side  of  each  section:  C.  Comma  tract 
of  Schultze.  //.  Olivospinal  tract  of  Helweg.  M.  Marginal  tract  of  Spitzka- 
Lissauer.     O.  Oval  field  of  Flechsig. 


or  margins  of  the  foramen  magnum  and  extends  to 
the  lower  border  of  the  first  lumbar  vertebra  below, 
from  which  point  it  is  continued  as  a  narrow  thread 
of  gray  substance,  the  filium  terminalis.  The  spinal 
cord  is  IS  to  20  inches  in  length,  and  weighs  one 
ounce.- 

The  columns  of  the  spinal  cord  are  divided  into  three 
chief  columns  or  funiculi.  The  ventral,  dorsal,  and 
lateral. 

The  columns  are  simply  connecting  pathways  for 
the  transmission  of  nerve  impulses  from  the  brain 
centres  to  spinal  centres,  and  contain  efferent,  afferent, 
and  association  fibers.  The  course  and  connecting 
pathways  of  these  nerve  fibers  within  the  white 
substance  is  seen  to  consist  of  numbers  of  medullated 


348  THE  NERVE  SYSTEM 

nerve  fibers,  without  possessing  any  neurilemma. 
They  run  in  a  vertical  direction,  and  with  their  sup- 
porting frame-work  of  neuroglia  and  connective  tissue — 
the  latter  is  derived  from  the  pia  mater  and  blood- 
vessels— are  grouped  into  bundles  of  axones,  termed 
columns  or  tracts,  which  are  marked  off  by  fissures 
that  can  be  seen  with  the  naked  eye  on  the  surface 
of  the  cord. 

The  Structure  of  the  Spinal  Cord. — If  a  cross-section 
of  the  spinal  cord  be  examined,  it  presents  a  central 
gray  substance  and  a  surrounding  white  substance, 
the  former  consisting  of  bodies  of  nerve  cells  and 
their  non-medullated  axones;  the  latter  contain  the 
medullated  axones  arranged  in  columns.  The  neuroglia 
pervades  both  the  white  and  gray  substance,  and  is 
the  supporting  tissue  frame-work  for  the  nerve  cells, 
their  dendrites,   and  axones. 

The  Gray  Substance  of  the  Cord. — It  is  arranged 
within  the  spinal  cord  in  the  form  of  two  crescents 
joined  in  the  centre,  or  a  figure  resembling  the  letter  H. 
The  gray  substance  on  either  side  extends  nearly  to  the 
surface  of  the  cord,  surrounded  by  the  white  matter, 
the  posterior  projections  are  called  the  dorsal  or 
posterior  horn,  and  the  anterior  the  ventral  or  anterior 
horn;  the  two  halves  of  the  gray  substance  are  con- 
nected by  a  bridge  of  gray  substance  termed  the 
commissure.  The  latter  presents  in  its  centre  a 
narrow  canal  (neural)  which  extends  the  entire  length 
of  the  cord.  It  is  lined  by  cylindric  epithelial  cells 
and  surrounded  by  a  gelatinous  material. 

The  anterior  horn  of  the  gray  substance  is  broader 
than  the  posterior,  and  is  completely  surrounded  by 
white  substance.  The  posterior  horn  is  narrower  and 
approaches  nearer  to  the  surface  of  the  cord  than  the 
anterior  horn  does,  and  is  enclosed  by  a  gelatinous 
substance  called  the  substantia  gelatinosa.  In  the 
lower  cervical  and  thoracic  portions  of  the  cord  the 


THE  CENTRAL  NERVE  SYSTEM  349 

gray  matter  is  expanded  into  a  projection  called  the 
lateral  horn.  This  is  seen  on  both  sides.  Microscopic 
examination  of  the  gray  substance  will  show  that  it 
is  practically  an  aggregation  of  neurones — nerve  cells 
with  their  dendrites  and  non-medullated  axones, 
lymphatics,  bloodvessels,  all  supported  in  a  frame- 
work of  non-neural  tissue — the  neuroglia. 

Classification  of  nerve  cells  within  the  gray  sub- 
stance as  regards  their  function:  They  are  divided 
into  intrinsic,  efferent,  and  afferent. 

The  intrinsic  cells  are  simply  associative  or  connec- 
tive in  character,  their  processes  enteV  the  white 
substance  horizontally,  and  give  off  branches  which 
ascend  -and  descend,  reentering  the  gray  substance 
at  different  levels,  where  their  axones  again  associate 
with  the  dendrites  of  other  intrinsic  cells. 

The  efferent  motor  cells  is  the  term  given  to  the 
cells  found  ni  the  anterior  horns,  which  are  sub- 
stations for  the  reception  from  the  brain  and  other 
neurones,  of  motor  impulses  which  they  in  turn 
conduct  through  their  efferent  axones,  to  the  periphery, 
and  promote  activity  in  the  muscles,  glands,  viscera, 
bloodvessels,  as  well  as  influence  the  growth,  develop- 
ment, and  metabolism  (trophic)  of  the  tissues. 

Afferent  cells  (sensor)  is  the  name  given  to  the 
cells  of  the  posterior  horn,  which  receive  from  the 
afferent  nerves  impulses  and  conduct  the  same  by 
their  afferent  axones,  to  the  cortex  of  the  brain,  giving 
rise  to  conscious  sensations,  as  heat,  pain,  sensation 
of  touch,  etc. 

The  Spinal  Nerves. ^ — There  are  thirty -one  pairs, 
divided  according  to  the  portion  of  the  cord  they 
arise  from,  as  follows:  * 

Cervical  pairs 8 

Thoracic  pairs 1^      V,  jAjfe^ 

Lumbar  pairs      ....-, .,  a^b..-  •  ^^.^^^1^     ' 

Sacral  pairs  .  ...       .    " !    ' .       ■  "'  ^^  * 

Coccygeal  pairs ^'l  . 

Total 3? 


350 


THE  NERVE  SYSTEM 


All  spinal  nerves  leave  the  spinal  canal  between  the 
vertebra  (intervertebral  foramen).  If  one  examines 
the  spinal  cord  after  removal,  the  spinal  nerves  will 
be  seen  to  consist  of  two  roots  by  which  they  arise 
from  the  sides  near  the  anterior  and  posterior  aspects 
of  the  cord.  The  two  roots  are  named  anterior  or 
ventral  and  posterior  or  dorsal.  The  anterior  and 
posterior  roots  join  to  form  a  single  nerve  trunk  just 
before  they  leave  the  spinal  canal.  The  dorsal  root 
presents  an  enlargement  near  the  point  at  which  it 
joins  the  anterior  root — a  small  grayish  body  called 
a  ganglion.  The  roots  do  not  leave  the  cord  as  a 
single  rounded  nerve,  but  are  formed  by  the  joining 
of  four  to  six  large  nerve  fibers. 


Fig.  125 


DORSAL    RO 


INAL   ROOT  GANGLION 


VENTRAL   FISSURE 

Showing  origin  of  two  pairs  of  spinal  nerves  (schematic).     (Gray.) 


The  posterior  root  is  sensor  or  afferent,  and  contains 
bundles  of  axones  which  convey  impulses  from  the 
end-organs  in  the  skin,  mucous  membranes,  etc., 
after  they  have  been  received  and  conveyed  by  axones 


THE  CENTRAL  NERVE  SYSTEM  351 

and  dendrites  of  the  ganglia  on  its  root,  to  the  groups 
of  cells  in  the  dorsal  horn  of  the  spinal  cord,  and  as 
we  have  mentioned  before,  these  impulses  ascend  and 
descend  by  means  of  collateral  branches,  axones,  and 
dendrites,  communicating  with  other  centres  in  the 
cord  at  different  levels  and  ultimately  reach  the 
sensor  areas  in  the  brain.  The  anterior  root  is  motor 
or  efferent,  and  contains  axones  which  transmit 
impulses  from  the  groups  of  cells  or  centres  in  the 
anterior  horn  of  the  spinal  cord,  which  are  further 
conveyed  by  means  of  the  efferent  axones  or  nerve 
fibers  to  the  periphery,  where  they  stimulate  muscles, 
glands,  viscera,  etc.,  into  activity. 

In  other  words,  motor  impulses  arise  in  the  cells  of 
the  anterior  horn  of  the  spinal  cord  and  the  motor  area 
in  the  brain,  and  are  conveyed  toward  the  periphery 
of  the  body  (muscles,  glands,  etc.),  by  means  of 
neurones  and  their  efferent  processes.  Sensor  impulses 
arise  within  the  structures  of  the  skin,  mucous  mem- 
brane, etc.,  and  are  conveyed  to  the  sensor  group  of 
cells  in  the  dorsal  horn  of  the  cord,  and  are  trans- 
mitted to  the  sensor  and  conscious  areas  in  the 
brain  by  aggregations  of  neurones  and  their  (afferent) 
processes  coursing  through  the  cord  and  brain  sub- 
stance. 

The  functions  of  the  spinal  cord  are  classified  under 
anatomatism,  reflex  action,  association  conduction,  sensor- 
conduction,  motor  conduction. 

Automatism,  or  Automatic,  Autochthonic  Action. — 
This  is  a  function  possessed  by  the  spinal  nerve  cells 
whereby  they  influence  the  growth,  development,  and 
nutrition  of  the  numerous  cells  of  the  various  tissues, 
and  thus  maintain  their  normal  physiologic  activity. 
By  this  expression  is  meant  a  discharge  of  energy 
from  the  cells  occasioned  by  a  change  in  their  environ- 
ment, i.  e.,  in  the  chemic  composition  of  the  blood  or 
lymph  by  which  they  are  surrounded,  and  independent 


352  THE  NERVE  SYSTEM 

of  any  excitation  coming  through  afferent  (sensor) 
nerves  from  the  periphery.  If  the  cell  activity  is 
continuous  it  causes  an  even  and  regular  control  over 
the  processes  of  cell  nourishment,  development,  etc. 
(trophic);  muscle  and  vascular  activity,  which  is 
spoken  of  as  tonus. 

Reflex  Actions. — They  are  defined  as  the  reception 
of  nerve  impulses  transmitted  to  the  nerve  cells  in 
the  spinal  cord  and  higher  centres  in  the  brain,  by 
afferent  (sensor)  nerves;  and  the  response  of  the  nerve 
cells  in  the  efferent  centres  to  this  stimulation,  which 
result  in  nerve  impulses  being  excited  in  the  nerve 
cells,  and  conveyed  by  the  efferent  (motor)  nerves, 
which  pass  from  these  cells  to  the  structures  to  be 
innervated,  and  cause  them  to  act,  as,  to  muscles, 
causing  contraction;  to  gland  cells,  secretion;  to 
bloodvessels,  increasing  or  decreasing  their  caliber; 
and  to  organs,  increasing  or  decreasing  their  activity. 

For  any  reflex  act  to  be  mechanically  possible  there 
must  be  present  the  following  structures: 

1.  A  surface  to  receive  the  stimuli:  skin,  mucous 
membrane,  sense  organ. 

2.  An  afferent  nerve  fiber  and  cell,  to  convey  the 
nerve-impulse  arising  as  a  result  of  the  stimulus 
exciting  the  sense  organ,  etc.,  into  activity. 

3.  An  emissive  cell,  from  which  arises  an  (4)  efferent 
nerve,  distributed  to  a  responsive  organ,  as  muscle, 
gland,  bloodvessel,  etc.  J^ 

In  a  more  practical  way  the  most  sinjple  reflex 
action  can  be  explained  as  follows:  If  a  muscle  is 
stimulated  by  a  strong  current  of  electricity  or  pinched 
by  an  instrument,  there  is  developed  in  the  terminals 
of  the  afferent  nerve  a  nerve  impulse  which  is  conveyed 
to  the  nerve  cells  in  the  posterior  horn  of  the  spinal 
cord,  the  dendrites  of  these  cells  transmit  the  impulse 
to  the  dendrites  of  the  nerve  cells  in  the^  anterior 
horn,   where   by   means   of   a   molecular  Jlliturbance 


THE  CENTRAL  NERVE  SYSTEM  353 

within  the  cells,  energy  is  liberated  and  the  nerve 
impulse  is  conveyed  by  the  efferent  nerve  to  the  muscle 
and  it  contracts. 

In  most  reflex  actions  there  is  and  must  be  a  more 
complex  arrangement  to  account  for  the  varied  move- 
ments and  functions  of  the  different  structures  of  the 
body  which  are  taking  place  in  response  to  external 
and  internal  stimuli.  These  complex  reflexes  are 
due  to  the  nerve  centres  in  the  cord  communicating 
by  means  of  axones  and  dendrites  of  other  cells  with 
other  higher  centres  at  different  levels  of  the  cord, 
not  only  on  the  same  but  the  opposite  side;  and  a 
still  more  complex  arrangement  is  produced,  due  to 
the  fact  that  the  centres  in  the  medulla  oblongata  are 
in  connection  with  the  spinal  centres  by  pathways 
of  nerve  fibers. 

Thus  reflex  actions  can  be  carried  on  without  the 
individual  being  conscious  thereof,  or  by  the  presence 
of  the  associated  neurones  other  centres  convey  sensa- 
tions to  the  brain,  of  which  we  are  conscious,  and  the 
return  impulse  can  excite  a  voluntary  movement. 

Reflex  actions  are  controlled  by  centres  in  the  brain 
(medulla)  which  transmit  impulses  to  the  spinal 
centres  which  either  decrease  or  inhibit,  either  increase 
or  accelerate  their  activity,  thus  regulating  the  recep- 
tion of  and  response  to  nerve  impulses  by  these 
centres  which  exert  a  controlling  influence  based  on 
the  needs  of  the  physiologic  functions  of  the  human 
body. 

Association  Conduction. — ^The  spinal  cord  is  divided 
into  segments  which  have  a  controlling  influence 
over  the  physiologic  functions  of  certain  parts  of  the 
body,  as  the  arm,  leg,  etc.  These  segments  to  properly 
work  together  and  receive  impulses  from  other  reflex 
centres  at  different  levels  in  the  cord,  which  control 
movements  in  response  to  stimuli  from  other  portions 
of  the  body,  are  held  in  communication  by  pathways 
23 


354  THE  NERVE  SYSTEM 

of  nerve  axones,  termed  association  fibers,  or  this 
phenomenon  is  spoken  of  as  association  conduction. 

Seiisor  Conduction. — This  term  is  used  in  speaking 
of  the  pathways  of  afferent  or  sensor  nerve  fibers  in 
the  tracts  of  the  spinal  cord,  which  convey  sensa- 
tions of  pain,  external  temperature,  thirst,  etc.,  from 
the  skin,  mucous  membranes,  etc.,  to  the  centres 
in  the  brain  directly  or  indirectly,  which  are  received 
by  nerve  cells  in  the  cortex,  giving  rise  to  conscious 
sensations.  These  afferent  pathways  are  not  thoroughly 
understood,  but  the  main  one  is  called  the  crossed 
pyramidal  tract. 

Motor  Conduction. — This  is  the  term  used  in  speak- 
ing of  the  pathways  of  efferent  or  motor  nerve  fibers 
in  the  tracts  of  the  spinal  cord  which  convey  motor 
impulses  from  the  cells  in  the  cortex  of  the  brain  to 
centres  in  the  spinal  cord,  that  transmit  nerve  impulses 
to  the  muscles,  glands,  etc.,  and  promote  their  activity. 
The  main  motor  pathway  is  called  the  direct  pyramidal 
tract. 


THE    ANATOMY    AND   PHYSIOLOGY   OF    THE 
BRAIN 

The  Brain  (Encephalon). — The  encephalon  or  brain 
is  that  part  of  the  cerebrospinal  system  which,  with 
its  membranes,  is  contained  in  the  cranium.  It  is 
composed  of  the  cerebrum,  cerebellum,  pons  Varolii, 
and  medulla  oblongata. 

The  Membranes  of  the  Brain. — These  are  the  dura, 
the  pia,  and  arachnoid. 

The  dura  mater  is  similar  in  structure  to  the  dura  of 
the  cord,  but  differs  from  it  in  being  closely  attached 
to  the  cranial  bones,  forming,  in  fact,  their  inner  peri- 
obleum.  It  is  continuous  with  that  of  the  cord  at  the 
foramen  magnum,  and  with  the  external  periosteum  of 


ANATOMY  AND  PHYSIOLOGY  OF  THE  BRAIN    355 

the  cranial  bones  by  means  of  its  prolongations  into 
the  many  foramina.  It  sends  in  various  processes  to 
support  and  separate  the  different  parts  of  the  brain, 
and  its  layers  separate  to  form  the  cranial  sinuses 
(venous).  In  the  vicinity  of  the  superior  longitudinal 
sinus  are  to  be  found,  on  its  outer  surface,  several 
glandulse  Pacchionii.  They  may  also  be  seen  on  its 
inner  surface  and  within  the  sinus,  as  well  as  on  the 
pia  mater. 

The  processes  of  the  dura  include  the  falces  cerebri 
et  cerebelli  and  the  tentorium  cerebelli. 

The  arachnoid  is  a  similar  membrane  to  that  of  the 
cord,  and  is  separated,  as  in  the  cord,  by  the  subarach- 
noid fluid  from  the  pia.  In  front  it  leaves  a  space 
between  it  and  the  pia  mater,  viz.,  along  the  pons 
and  interpeduncular  region,  the  anterior  subarach- 
noid space;  and  behind,  between  the  medulla  and 
and  the  cerebellum,  is  a  second  interval  called  the 
posterior  subarachnoidean  space.  Both  are  connected 
with  the  ventricles  of  the  brain  by  the  foramen  of 
Majendie  in  the  pia  mater  covering  the  fourth  ven- 
tricle. 

The  pia  mater  is  a  very  vascular  delicate  membrane 
which  dips  into  the  sulci  and  forms  the  various 
choroid  plexuses  and  also  the  velum  of  the  third 
ventricle.  The  vessels  of  the  brain  run  in  the  pia 
mater  before  entering  the  brain. 

The  brain,  for  purposes  of  description,  includes  the 
cerebrum,  cerebellum,  medulla  oblongata,  and  pons 
varolii. 

Medulla  Oblongata. — The  medulla  oblongata  is  a 
pyramidal  body,  |  to  1  inch  long,  along  its  ventral 
surface,  and  f  inch  thick.  Its  larger  extremity  is 
continuous  with  the  pons  above;  its  smaller  extremity, 
directed  downward  and  backward,  blends  with  the 
spinal  cord  below.  The  anterior  surface  lies  on  the 
basilar  groove  of  the  occipital  bone. 


356  THE  NERVE  SYSTEM 

In  front  and  behind  it  is  marked  by  the  continuation 
of  the  anterior  and  posterior  median  fissures  of  the 
cord,  the  former,  with  its  process  of  pia  mater,  ending 
in  a  cul-de-sac  just  below  the  pons,  the  foramen  cecum. 
The  posterior  expands  into  the  fourth  ventricle. 

Each  lateral  half  of  the  medulla  is  divided  into 
areas. 

The  Areas  of  the  Medulla  Oblongata. — These 
are:  (1)  Ventral  area;  containing  the  pyramid.  (2) 
Lateral  area;  containing  the  lateral  tract  olive.  (3) 
Dorsal  area;  containing  the  funiculus  gracilis,  funiculus 
cuneatus,  funiculus  lateralis,  and  tuberculum  cinereum. 

The  restiform  body  succeeds  the  gracile  and  cuneate 
nuclei  in  the  dorsolateral  part  of  the  medulla  oblongata. 
Its  fibers  converge  from  various  sources  and  ultimately 
enter  the  cerebellum  as  its  inferior  peduncle.     (Gray.) 

The  Decussation  of  the  Pyramids.  It  is  a  term 
applied  to  the  interlacing  bundles  seen  on  the  ventral 
aspect  of  the  medulla,  at  the  junction  of  the  medulla 
and  the  spinal  cord.  Ninety  per  cent,  of  the  fibers 
cross  the  median  line  in  this  decussation  to  continue 
as  the  crossed  pyramidal  tract. 

Structure  of  the  Medulla  Oblongata. — Gray 
and  white  matter  are  constituents  of  the  medulla; 
the  former  is,  in  the  internal  part,  continuous  with 
the  gray  substance  of  the  cord,  while  the  white 
substance  is  external. 

The  Gray  substance  of  the  medulla,  examined  under 
the  microscope,  presents  numerous  groups  of  nerve 
cells  similar  in  arrangement  to  the  cells  in  the  spinal 
cord,  but  they  are  not  so  regular,  due  to  the  changed 
course  of  the  fibers  of  the  white  substance.  These 
nerve  cells  are  supported  by  neuroglia  and  connective 
tissue.  The  nerve  cells  give  off  axones  which  ascend 
to  the  brain  and  descend  to  the  cord,  conveying  nerve- 
impulses  to  the  brain  (sensor  or  conscious),  and 
transmitting  other  impulses  from  the  brain  to  the 


ANATOMY  AND  PHYSIOLOGY  OF  THE  BRAIN    357 

cord  (motor  or  volitional),  and  others  give  off  axones 
which  form  portions  of  the  cranial  nerves. 

The  white  substance  is  composed  of  bundles  of  nerve 
fibers  supported  by  a  frame-work  of  neuroglia  and 
connective  tissue.  These  columns  formed  of  bundles 
of  nerve  fibers  are  the  connecting  or  conducting 
pathways  coursing  from  the  brain  to  the  spinal  cord, 
for  the  transmission  of  nerve  impulses  between  the 
brain  and  the  periphery. 

The  Pons  Varolii. — ^The  pons  is  a  white  mass  on  the 
anterior  aspect  of  the  brain  stem  placed  between  the 
medulla  oblongata  and  the  crura  cerebri.  It  is  convex 
from  side  to  side,  containing  mostly  transverse  and 
longitudinal  fibers.  The  transverse  fibers  are  collected 
into  rounded  bundles,  to  continue  as  the  middle 
peduncles  into  the  white  substance  of  the  correspond- 
ing cerebellar  hemispheres.  The  middle  peduncles  are 
commissural  paths  consisting  of  axones  coursing  in 
opposite  directions  connecting  the  nuclei  with  the 
cerebellum;  then  some  axones  pass  into  the  opposite 
middle  peduncle,  forming  uninterrupted  commissural 
systems;  again,  a  few  fibers  communicate  with  nuclei 
in  the  brain  stem,  notably  the  oculomotor,  trochlear, 
and  abducent  cranial  nerves. 

The  Structure  of  the  Pons  Varolii. — It  consists  of  a 
central  gray  and  white  mass  of  nerve  tissue,  supported 
by  neuroglia  and  connective  tissue.  Microscopically, 
bundles  of  nerve  fibers  and  nerve  cells  can  be  seen 
in  groups,  the  former  coursing  in  a  longitudinal  and 
transverse  direction,  as  continuations  of  the  pathways 
of  nerve  fibers  from  the  cord  and  medulla  below, 
and  the  cerebrum  and  cerebellum  above.  The  trans- 
verse bundles  of  nerve  fibers  in  the  pons  convey 
impulses  from  the  corresponding  and  opposite  hemi- 
spheres of  the  brain.  The  nerve  cells  in  the  pons  give 
off  axones  w^hich  form  some  of  the  cranial  nerves. 

Functions  of  the  Medulla  Oblongata  and  Pons 
Varolii.— The   medulla   and   pons   contain   tracts   of 


358  THE  NERVE  SYSTEM 

nerve  fibers  which  convey  impulses  from  the  brain 
and  cerebellum  to  the  spinal  cord.  The  anterior 
portion  of  the  medulla  and  pons  contain  pathways 
for  the  transmission  of  volitional  efferent  nerve 
impulses  from  the  higher  centres  in  the  brain  to  the 
spinal  cord;  the  posterior  portion  contains  pathways 
for  the  conduction  of  afferent  nerve  impulses  from 
the  spinal  cord  to  the  brain.  The  medulla  and  pons 
contain  groups  of  nerve  cells  and  nerve  fibers,  called 
nerve  centres,  which  are  in  connection  with  and  can 
be  influenced  reflexly  by  other  nerve  impulses  received 
from  associated  groups  of  nerve  fibers. 

The  Cerebellum. — The  cerebellum  is  the  largest  portion 
of  the  hind-brain.  It  lies  in  the  posterior  fossa  of  the 
skull  separated  from  the  occipital  lobes  of  the  cere- 
brum by  the  tentorium  cerebelli.  It  is  behind  the 
pons  and  medulla  oblongata,  connected  with  the 
former  through  the  middle  peduncles,  and  partly 
embracing  the  latter;  and  connected  with  the  restiform 
body  (medulla)  by  means  of  the  inferior  peduncles; 
the  superior  peduncles  contain  fibers  which  pass  from 
the  cerebellum  to  the  tegmentum  of  the  midbrain  in 
front. 

The  cerebellum  is  divided  into  a  medial  segment, 
the  vermis  or  worm;  two  lateral  hemispheres;  a  ventral 
and  dorsal  notch;  and  a  superior  and  inferior  surface; 
and  is  subdivided  into  lobes  and  fissures. 

The  arbor  vitse  is  the  name  given  to  the  arrangement 
of  the  white  substance  of  the  cerebellum,  seen  on  a 
median  section.  The  cerebellum  weighs  5.8  ounces  in 
the  male;  and  5.4  ounces  in  the  female.  The  propor- 
tion between  the  cerebellum  and  cerebrum  is  1  to  7.5 
in  the  adult;  1  to  8.5  among  eminent  men;  1  to  20  in 
the  newborn.     (Gray.) 

The  Structure  of  the  Cerebellum. — Examined  on  a 
cross-section,  the  cerebellum  consists  of  gray  and 
white  matter.    The  gray  matter  is  external  with  the 


ANATOMY  AND  PHYSIOLOGY  OF  THE  BRAIN    359 

white  matter  in  the  centre.  The  gray  substance 
consists  of  masses  of  nerve  cells,  their  axones,  and 
dendrites.  The  cells  are  arranged  in  layers.  The  white 
matter  consists  of  nerve  fibers  which  pass  in  different 
directions  and  connect  various  portions  of  the  cere- 
bellum with  one  another.  Nerve  fibers  are  grouped 
in  bundles  and  connect  cerebellum  with  the  cerebrum, 
pons  varolii,  medulla  oblongata,  and  spinal  cord. 

I'he  Function  of  the  Cerebellum. — It  is  the  centre 
for  maintaining  the  equilibrium  of  the  body,  by 
sending  out  nerve  impulses,  which  cause  a  combined 
action  of  groups  of  muscles  that  enable  the  body  to 
stand  erect  without  swaying,  and  assist  in  the  various 
and  complex  movements  seen  in  walking,  dancing, 
running,  etc.  The  centres  in  the  cerebellum  are 
reflexly  influenced  by  nerve  impulses  arising  in  the 
end-organs  of  the  skin,  retina  of  the  eye,  tactile  (touch) 
sense,  and  the  labyrinth  of  the  ear.  These  impulses 
are  transmitted  to  the  cerebellum  by  afferent  nerve 
fibers  and  they  stimulate  the  centres  to  activity  and 
the  nerve  impulses  are  conveyed  by  efferent  nerves, 
though  the  pons,  medulla,  and  spinal  cord  and  nerves 
to  the  general  muscle  system. 

The  Cerebrum. — The  cerebrum  is  the  largest  part  of 
the  brain,  and  consists  of  two  lateral  halves  or  hemi- 
spheres, separated  by  the  great  longitudinal  fissure 
and  connected  to  each  other  by  a  great  commissure, 
the  corpus  callosum.  The  latter  constitutes  a  great 
system  of  association  nerve  fibers  for  the  bilateral 
coordination  of  corresponding  parts  of  the  nerve  cells 
in  the  cortex.  The  hemispheres  are  subdivided  into 
lobes,  and  the  latter  present  over  their  entire  surfaces 
convoluted  eminences,  the  gyri  or  convolutions,  sepa- 
rated by  depressions,  the  sulci  or  fissures.  (See  Figs. 
126  and  127.) 

The  cerebrum,  as  a  whole,  is  convex  from  before 
backw^ard  and  from  side  to  side,  narrower  in  front 


360 


THE  NERVE  SYSTEM 


Fig.  126 


Fissures  and  gyres  of  the  lateral  surface  of  the  left  hemicerebrum.     (Gray  ) 


Fig.  127 


G.  =  GYRE 
F  =  FISSURE 


Fissures  and  gyres  of  the  mesal  surface  of  the  left  hemicerebrum.     (Gray.) 


ANATOMY  AND  PHYSIOLOGY  OF  THE  BRAIN    361 

than  behind.  Its  inferior  surface  is  flattened  and 
overlaps  the  midbrain  and  cerebellum,  from  which  it 
is  separated  by  the  tentorium  cerebelli.  The  outer 
surface,  including  the  fissures,  is  composed  of  gray 
matter,  the  cortical  substance,  while  the  interior  is 
of  white  matter. 

Lobes  of  the  Cerebrum.  —  The  lobes  are  the 
frontal,  the  parietal,  the  occipital,  the  temporal,  and 
the  central  lobe  or  Island  of  Reil. 

The  Frontal  Lohe. — The  lateral  surface  is  separated 
behind  from  the  parietal  lobe  by  the  central  fissure  or 
the  fissure  of  Rolando,  and  below,  from  the  temporal 
lobe  by  the  Sylvian  fissure,  in  part,  and  rests  on  the 
orbital  plate  of  the  frontal  bone. 

The  Parietal  Lobe. — The  lateral  surface  is  bounded 
in  front  by  the  central  fissure,  below  by  the  Sylvian 
fissure,  above  by  the  back  part  of  the  internal  border; 
it  is  only  partially  separated  from  the  occipital  lobe 
by  the  occipital  fissure,  merging  gradually  into  the 
temporal  lobe. 

The  Occipital  Lobe.— The  lateral  surface  is  bounded 
anteriorly  by  the  occipital  fissure,  which  partially 
separates  it  from  the  parietal  lobe,  also  the  para- 
occipital  and  exoccipital  fissures  are  seen  extending 
into  the  lobe. 

The  Temporal  Lobe. — The  lateral  surface  is  bounded 
by  the  basisylvian  and  Sylvian  fissures  and  by  the 
ventrolateral  border;  posteriorly,  it  merges  into  the 
adjacent  parietal  and  occipital  lobes. 

The  Island  of  Reil  (central  lobe  or  insula). — This  is 
seen  after  separating  the  lips  of  the  sylvian  cleft, 
after  raising  the  frontal  lobe;  it  is  overlapped  by  the 
opercula;  the  latter  removed,  the  island  of  Reil  is 
seen  as  a  tetrahedral-shaped  mass  with  its  apex 
directed  forward  and  upward. 

The  Rhinencephalon  or  Olfactory  Lobe.  —  This  con- 
stitutes  the   central   olfactory   structures,    as   distin- 


362 


THE  NERVE  SYSTEM 


guished  from  the  rest  of  the  fore-brain.  It  comprises: 
(1)  Peripheral  parts;  (2)  central  or  cortical  portions; 
the  former  is  divided  into  pre-  and  postolfactory 
portions. 

The  Ventricles  of  the  Brain. — The  ventricles 
of  the  brain  are  narrow  cavities  enclosed  with  the 
substance  of  the  cord.     They  are  filled  with  cerebro- 

FiG.  128 


rORAMCN    OF    MONRO 


MIDDLE    COMMISSURE 

CHOROID    PLEXUS    OF 
THIRD   VENTRICLE 

TAENIA   THALAMI 


ROSTRUM' 

COPULA 

ANTER 

COMMISSI 

LAMINA    TERII 


PITUITARY    BODY 


AQUEDUCT 
SUP      MCOULLAF 
VELUM 
FOURTH 


VENTRICLE 

Mesal  aspect  of  a  brain  sectioned  in  the  median  sagittal  plane. 


spinal  fluid  and  communicate  with  one  another  by 
means  of  narrow  canals  and  foramen.  The  ventricles 
are  called  the  lateral,  third,  and  fourth. 

The  lateral  ventricles  are  serous  cavities,  have  a 
thin  lining  membrane  covered  by  a  layer  of  epithelium 
cells  (ependyma),  which  secretes  a  serous  fluid.  They 
are  contained  one  in  each  hemisphere,  separated  by 


ANATOMY  AND  PHYSIOLOGY  OF  THE  BRAIN    363 

the  septinii  lucidum,  and  each  is  divided  into  a  body 
and  three  corny  a,  an  anterior,  posterior,  and  middle. 
The  foramen  of  Monro  connects  them  with  the  third 
ventricle. 

The  third  ventricle  is  derived  from  the  primitive 
fore-brain  vesicle,  except  that  portion  which  also 
enters  into  the  formation  of  the  lateral  ventricles.  It 
is  a  narrow  space  between  the  two  thalami  and  hypo- 
thalamic gray,  limited  in  front  by  the  terma,  behind 
continuous  with  the  aqueduct  of  Sylvius,  and  laterally 
is  continuous  with  the  lateral  ventricles  through  the 
foramen  of  Monro. 

The  fourth  ventricle  is  an  irregularly  pyramidal- 
shaped  cavity,  with  a  lozenge-shaped  base,  and  ridge- 
like apex;  found  between  the  medulla  oblongata  and 
the  back  part  of  the  pons  varolii  in  front  and  the 
cerebellum  behind.  It  is  divided  into  a  roof  and  a 
floor.  Below  the  fourth  ventricle  is  continuous  with  the 
small  central  canal  of  the  cord  and  post-oblongata 
(in  part);  above  it  communicates  with  the  third 
ventricle  by  means  of  the  aqueduct  of  Sylvius.  The 
fourth  ventricle  has  an  opening  through  the  tela 
choroidea,  which  permits  of  communication  with 
the  subarachnoid  space;  it  is  called  the  foramen  of 
Majendie. 

The  Structure  of  the  Cerebrum. — It  consists 
of  masses  of  gray  and  white  substance.  The  gray 
being  outside,  makes  up  the  cortex.  The  gray  sub- 
stance is  composed  of  layers  of  nerve  cells  and  nerve 
fibers,  with  their  axones  and  dendrites  embedded  in 
a  net-work  of  neuroglia.  The  nerve  fibers  may  be 
amyelinic  or  myelinic.  Their  direction  may  be  either 
transverse  or  vertical. 

The  white  substance  of  the  cerebrum  is  composed 
of  myelinic  nerve  fibers  interwoven  into  an  intricate 
series  of  pathways,  which  are  classified  into  (1)  asso- 
ciation fibers,  which  connect  neighboring  or  distant 


364  THE  NERVE  SYSTEM 

portions  with  the  same  half  of  the  cerebrum;  (2) 
commissural  fibers  which  pass  between  the  two 
halves  of  the  cerebrum  and  connect  similar  areas 
within  each;  they  cross  in  the  middle  line  of  the 
brain  and  form  commissures;  (3)  projecting  fibers, 
which  connect  the  cerebrum  with  lower  nerve  centres 
in  the  brain  and  spinal  cord,  and  other  fibers  that 
connect  the  lower  centres  with  the  brain. 

The  Weight  of  the  Brain. — The  average  weight  of 
the  human  brain  in  the  adult  male  is  1400  grams 
(49.5  ounces);  in  the  female,  1250  grams  (44  ounces); 
in  the  newborn,  400  grams  (14.1  ounces). 

The  Functions  of  the  Cerebrum. — The  functions 
of  the  cerebrum  have  been  discovered  as  a  result  of 
a  study  of  the  anatomic  development  of  the  brain, 
and  examination  of  brains  of  various  animals,  human 
beings,  etc.,  and  a  study  of  diseases  or  injured  brains, 
certain  parts  of  which  have  been  rendered  inactive 
by  the  destruction  of  nerve  cells  and  their  processes; 
such  a  destruction  of  tissue  has  been  manifested  in 
different  parts  of  the  body  by  an  interference  or  loss 
of  the  function  of  the  ex^tremity,  etc.,  to  which  the 
nerve  leading  from  or  to  the  diseased  region  in  the 
brain  is  distributed.  Thus  it  has  been  determined 
that  certain  areas  of  the  brain  contain  nerve  cells 
and  nerve  fibers  which  control  definite  functions  of 
the  body,  and  are  grouped  into  definite  areas,  irregu- 
larly marked  oft'  by  fissures,  and  correspond  to  the 
convolutions  seen  on  the  surface  of  the  cerebrum. 
These  areas  are  spoken  of  as  the  cortical  localization 
of  function. 

Cortical  Localization  of  Functio7i} — Motor  Area. — 
Comprises  the  precentral  gyre  and  parts  of  the  frontal 
gyres  adjacent  thereto,  together  with  the  paracentral, 
and  the  adjacent  portion  of  the  superfrontal  gyre  on 
its  inner  aspect.     This  area  comprises  the  centres  for 

1  See  Figs.  129  and  130,  page  365. 


ANATOMY  AND  PHYSIOLOGY  OF  THE  BRAIN    365 

the  muscle  control  of  the  following  parts  of  the  body 
located  as  follows: 

Fig.  129 


Lateral  view  of  left  cerebral  hemisphere,  showing  localization  of  functions 
(Gray.) 

Fig.  130 


Mesal  view  of  left  cerebral  hemisphere,  showing  localization  of  functions. 


366  THE  NERVE  SYSTEM 

Lower  Limbs. — Back  part  of  precentral  and  para- 
central fissures. 

Trunk. — Toward  the  front  part,  both  on  the  under 
and  in  the  back  superfrontal  fissure. 

Upper  Limbs. — Midportion  of  precentral  fissure. 

Facial. — Front  part  of  precentral  fissure. 

Tongue,  Larynx,  Muscles  of  Mastication,  Pharyiix. — 
Frontal  opercular  part. 

Movements  of  Head  and  Eye. — Medifrontal  fissure, 
adjacent  to  precentral  fissure. 

Owing  to  a  decussation  of  the  pyramidal  (motor) 
tracts  in  their  course  to  the  primary  motor  centres, 
the  motor  centres  in  one  cerebral  hemisphere  control 
the  movements  of  the  opposite  side  of  the  body. 

Sensor  Areas. — Tactile  and  temperature  impressions. 
Postcentral  fissure,  in  corresponding  order  with  the 
neighboring  precentral  motor  area;  the  postcentral 
(sensor)  and  precentral  (motor)  fissures  are  so  closely 
associated  in  the  highest  category  of  the  reflex  arc 
system  represented  in  the  cerebral  cortex,  that  they 
are  included  under  the  term  of  somesthetic  or  senso- 
motor  area  devoted  to  the  registration  of  cutaneous 
impi;essions,  impressions  from  the  muscles,  tendons, 
and  joints;  in  short,  the  sense  of  movement. 

Stereognostic  Sense  Area  (concrete  perception  of  the 
form  and  solidity  of  objects). — Parietal  fissure  and 
its  extension  in  the  precuneus  on  the  inner  aspect. 

Auditory  ^rm.^Middle  third  of  supertemporal,  and 
adjacent  transtemporal  fissures  in  the  Sylvian  cleft. 

Visual  Area. — Calcarine  fissure  and  cuneus  as  a  whole. 

Olfactory  Area. — Uncus,  frontal  part  of  hippocampus, 
indusium,  subcallosal  fissures,  parolfactory  area,  and 
anterior  perforated  substance. 

Gustatory  Area. — Probably  in  region  of  the  olfactory 
area  in  the  temporal  lobe  (uncinate  and  hippocampal 
fissures  ?)  (not  definitely  settled). 

Language  Areas.^ — Emissive  (articular)  centre  for 
speech   (control   of  muscles   used   in   speech;  larynx, 


ANATOMY  AND  PHYSIOLOGY  OF  THE  BRAIN    367 

tongue,  jaw  muscles).  Junction  of  subfrontal  fissure 
with  the  precentral  fissure. 

Auditory  Perceptive  Centre  (word  deafness,  also  the 
lalognostic  or  word  understanding  centre). — Marginal 
fissure  and  adjacent  parts  of  super-  and  meditemporal 
fissure. 

Visual  Receptive  Centre  (word  blindness). — Angular 
fissure. 

Emissive  "  Writing''  Centre. — Medifrontal  fissure, 
in  front  of  motor  area  for  the"  upper  limb  (this  has  not 
been  definitely  proved  or  accepted). 

Language  Arrangement  Centre. — Island  of  Reil  or 
insular  association  area  serving  to  connect  the  various 
receptive  sense  areas  relating  to  the*  understanding 
of  the  written  and  spoken  word  with  the  somesthetic 
sensormotor  emissary  centre  related  to  articulate 
speech  and  writing. 

Association  Areas. — lender  this  heading  are  included 
the  frontal  association  area  concerned,  so  far  as  is 
known,  with  the  powers  of  thought  in  the  abstract, 
creative,  constructive,  philosophic,  the  seat  of  the  will, 
memory.  The  parieto-occipito-temporal  area  is  con- 
cerned with  the  powers  of  conception  of  the  concrete, 
for  the  comprehension  of  analogies,  comparing,  gen- 
eralizing, and  systematizing  things  heard,  observed, 
and   felt    (Gray) . 

Sleep. — Different  theories  have  been  proposed  to 
account  for  the  causes  of  sleep,  none  of  which  has 
been  wholly  satisfactory. 

The  most  generally  accepted  theory  is  based  on  the 
decline  in  the  irritabihty  of  the  nerve  cells  of  the  brain 
and  associated  sense  organs,  and  the  development  of 
fatigue  conditions,  the  result  of  prolonged  activity 
(Brubaker).^ 

The  Peripheral  Nerve  System. — The  peripheral 
nerve    system    includes    those    nerve    trunks   which 

^  See  chapter  on  arteries  and  veins  for  blood-supply  of  brain  and 
its  membranes. 


368  THE  NERVE  SYSTEM 

convey  impulses  to  and  from  the  centres  in  the  brain 
to  the  structures  of  the  body.  They  are  divided  into 
cranial  nerves,  which  do  not  pass  through  the  spinal 
cord,  but  leave  the  brain  direct  from  various  locations; 
and  spinal  nerves,  which  derive  their  nerve  fibers 
from  the  spinal  cord  and  pass  out  of  the  spinal  canal 
by  way  of  the  foramen  between  the  vertebra. 

The  Cranial  Nerves. — The  cranial  nerves  consist  of 
twelve  pairs,  as  follows : 

I.  Olfactory  (fila). 
II.  Optic. 

III.  Oculomotor. 

IV.  Trochlear. 
V.  Trigeminal. 

VI.  Abducent. 
VII.  Facial. 

Nervus  intermedins. 
VIII.  Acoustic. 

1.  Cochlearis. 

2.  Vestibularis. 
IX.  Glossopharyngeal. 

X.  Vagus. 
XI.  Spinal  accessory. 

1.  Accessory  to  vagus. 

2.  Spinal  part. 
XII.  Hypoglossal. 

These  nerves  have  each  a  superficial  and  a  deep 
origin.  The  former  corresponds  to  its  point  of  attach- 
ment at  the  surface  of  the  brain;  the  latter  to  certain 
nuclei  or  collections  of  nerve  cells  in  the  structure  of 
the  brain.  The  superficial  origin  only  will  be  men- 
tioned. 

The  Olfactory  Nerves  (First). — ^The  olfactory 
nerves  or  fila  are  the  special  nerves  of  the  sense  of 
smell.  Twenty  in  number  on  each  side.  They  are 
distributed  to  the  olfactory  region  in  the  upper  part 


ANATOMY  AND  PHYSIOLOGY  OF  THE  BRAIN    369 

of  the  superior  turbinated  process  of  the  ethmoid  and 
corresponding  portion  of  the  nasal  septum.  These 
filaments  represent  the  axones  of  the  olfactory  cells 

Fig.  131 


r»  mtal  lobe. 


Occipital 
lobe. 


Base  of  brain,  showing  superficial  origin  of  cranial  nerves. 


and  pass  through  the  cribiform  plate  of  the  ethmoid 
bone  to  join  the  under  surface  of  the  olfactory  bulb, 
which  rests  on  the  cribriform  plate,  and  is  the  oval  mass 
of  a  grayish  color  that  forms  the  anterior  extremity 
24  "^ 


370  THE  NERVE  SYSTEM 

of  a  slender  process  of  brain  substance,  called  the 
olfactory  tract.  The  olfactory  nerves  differ  in  struc- 
ture from  the  other  nerves,  containing  only  amyelinic 
fibers. 

The  Optic  .Nerves  (Second). — ^The  fibers  of  the 
optic  nerves,  the  special  nerve  of  the  sense  of  sight, 
are  situated  in  the  retina;  they  start  as  the  central 
processes  of  the  ganglion  cells  which  converge  and 
pierce  the  choroid  and  sclera  as  a  cylindric  cord.  The 
point  of  emergence  is  situated  a  little  internal  to  the 
posterior  pole  of  the  globe.  Passing  through  the  orbital 
fat,  in  an  inward  and  backward  direction,  it  passes 
through  the  optic  foramen  to  end  in  the  optic  chiasm 
or  commissure.  The  optic  chiasm  is  somewhat  quadri- 
lateral in  shape,  rests  on  the  olivary  eminence  and  the 
diaphragma  sellse,  being  bounded  above  by  the  lamina 
terminalis;  behind,  by  the  tuber  cinereum,  on  either 
side  by  the  anterior  perforated  substance.  Within 
the  chiasm  the  fibers  cross  as  follows:  Those  from 
the  nasal  side  of  the  left  and  right  halves  of  the  retina 
cross  in  the  centre,  to  the  opposite  optic  tract;  those 
from  the  temporal  side  of  the  right  and  left  eyes  pass 
backward  without  crossing,  to  end  in  the  optic  tract 
of  the  same  side. 

The  optic  tract  passes  back  to  areas  of  the  brain 
where  the  nerve  impulses  are  conveyed  to  the  cuneus 
(the  area  for  the  sense  of  sight  in  the  cortex)  by  means 
of  another  pathway,  the  optic  radiation.  By  connections 
with  other  nerve  centres  in  the  brain  the  optic  tract 
communicates  with  the  origin  of  the  nerves  which 
influence  the  muscles  that  control  the  movements  of 
the  eye-ball. 

The  Oculomotor  (Third). — The  oculomotor  arises 
superficially  from  the  crus  anterior  to  the  pons,  its 
deep  origin  being  a  gray  nucleus  in  the  floor  of  the 
aqueduct  of  Sylvius.  It  runs  to  the  outer  side  of  the 
posterior  clinoid  j)r()(TSs  of  the  sphenoid  bone,  enters 


ANATOMY  AND  PHYSIOLOGY  OF  THE  BRAIN    371 

the  cavernous  sinus,  runs  above  the  other  nerves  in 
its  outer  wall,  and  divides  into  two  branches,  which 
enter  the  orbit  between  the  two  heads  of  the  external 
rectus.  It  is  joined  in  the  sinus  by  sympathetic  fila- 
ments. The  superior  branch  crosses  the  optic  nerve 
to  supply  the  superior  rectus  and  levator  palpebrse 
muscles.  The  inferior  divides  into  three  parts — one 
for  the  inferior  oblique,  one  to  the  inner,  and  one  to 
the  lower  recti  muscles.  The  first  supplies  the  motor 
root  of  the  lenticular  ganglion  of  the  sympathetic 
system. 

The  Trochlear  (Fourth). — The  trochlear  nerve 
has  an  apparent  origin  from  the  upper  side  of  the 
valve  of  Vieussens,  and  a  deep  from  the  floor  of  the 
aqueduct  of  Sylvius.  The  two  nerves  communicate 
by  a  transverse  band  on  the  valve  of  Vieussens.  The 
nerve  pierces  the  dura  after  crossing  over  the  crus, 
enters  the  cavernous  sinus,  in  whose  outer  wall  it  lies 
between  the  ophthalmic  and  third  nerves,  then  crosses 
the  latter  to  enter  the  orbit  through  the  sphenoidal 
fissure  above  the  external  rectus,  and  enters  the 
superior  oblique  muscle. 

The  Fifth  Nerve  (Trifacial). — The  fifth  or 
trifacial  is  the  largest  of  all  the  cranial  nerves,  and 
arises  by  two  roots,  a  motor  and  a  sensor.  The  former 
is  small,  and  the  latter  has  the  Gasserian  ganglion 
upon  it.  Both  arise  from  the  side  of  the  pons  super- 
ficially, the  smaller  root  above  the  larger,  some  trans- 
verse fibers  of  the  pons  separating  the  two.  This 
nerve  conveys  both  motion  and  sensation.  At  the 
apex  of  the  petrous  portion  of  the  temporal  the  large 
root  forms  the  Gasserian  ganglion;  the  smaller  does 
not  join  in  the  ganglion,  but  runs  below  it  to  join, 
just  below  the  foramen  ovale,  the  lowest  trunk  pro- 
ceeding from  the  ganglion. 

The  Gasserian  ganglion  lies  in  a  hollow  near  the  apex 
of  the  petrous  portion  of  the  temporal  bone,  the  large 


372 


THE  NERVE  SYSTEM 


superficial  petrosal  nerve,  and  the  motor  root  lying 
below    it.      It    receives    branches    from    the    carotid 


Fig.  132 


Sensory  root: 
Motor  root. 


Auriculo-temporal 
tierpe. 


Distribution  of  the  second  and  third  divisions  of  the  fifth  nerve  and 
submaxillary  gangHon.     (Gray.) 


plexus.  Small  twigs  pass  to  the  dura  mater.  This 
ganglion  sends  off  three  large  branches,  viz.,  the 
ophthalmic,  superior  maxillary,  and  inferior  maxillary. 


ANATOMY  AND  PHYSIOLOGY  OF  THE  BRAIN    373 

The  first  two  confer  sensation,  the  third,  motion 
and  sensation. 

The  ophthalmic  nerve,  or  first  division  of  the  fifth 
nerve,  is  sensor  and  the  smallest  branch  of  the  ganglion. 
It  is  flattened,  about  1  inch  long.  It  receives  filaments 
from  the  cavernous  plexus,  and  gives  off  filaments  to 
the  third  and  sixth,  and  sometimes  to  the  fourth  nerve, 

Fia.  133 


Internal  carotid  artery 
and  carotid  plexus. 


Nerves  of  the  orbit  and  ophthalmic  ganglion.     Side  view.     (Gray  ) 


and  a  recurrent  branch  running  in  the  tentorium  cere- 
belli  with  the  fourth.  Finally,  it  divides  into  the 
frontal,  lacrymal,  and  nasal  nerves,  which  pass  through 
the  sphenoidal  fissure  into  the  orbit. 

The    second    division    of    the    fifth    nerve    (superior 
maxillary)  is  sensor,  and  enters  the  foramen  rotundum. 


374  THE  NERVE  SYSTEM 

crosses  the  sphenomaxillary  fossa,  and,  as  the  infra- 
orbital, traverses  the  canal,  emerges  from  the  foramen 
to  end  on  the  face  in  .the  palpebral,  nasal,  and  labial 
branches — the  first  set,  to  lower  lid;  the  second,  to 
side  of  nose;  and  the  third,  to  upper  lip. 

The  orbital  or  temporomalar  branch  enters  the  orbit 
by  the  sphenomaxillary  fissure,  and  divides  into  two 
branches,  which  pierce  the  malar  bone. 

The  alveolar  or  superior  dental  nerves  are  three: 
The  posterior,  middle,  and  anterior,  which  supply  the 
upper  row  of  teeth. 

The  inferior  maxillary  nerve  (third  division  of  the 
fifth)  is  the  largest  branch,  and  arises  by  two  roots — 
a  large  sensor  root  from  the  Gasserian  ganglion  and 
the  motor  root  of  the  fifth.  This  nerve  divides  into 
two  trunks,  anterior  and  posterior.  The  anterior  gives 
off  the  masseteric,  the  buccal,  the  deep  temporal,  and 
the  two  pterygoid  nerves. 

The  posterior  trunk  of  the  inferior  maxillary  is 
mostly  sensory.  It  divides  into  the  auriculotemporal, 
gustatory,  and  inferior  dental;  the  last  supplies  the 
lower  row  of  teeth. 

The  gustatory  or  lingual  nerve  lies  at  first  beneath 
the  external  pterygoid,  internal  to  the  dental  nerve. 
Here  a  branch  from  the  dental  may  cross  the  internal 
maxillary  to  join  it.  The  chorda  tympani  also 
joins  it. 

The  nerve  now  runs  along  the  inner  side  of  the 
ramus  of  the  jaw,  and  crosses  the  upper  constrictor  to 
the  side  of  the  tongue  above  the  deep  part  of  the 
submaxillary  gland;  lastly,  it  runs  below  Wharton's 
duct,  and  superficially  along  the  side  of  the  tongue  to 
its  apex.  It  communicates  with  the  facial  through 
the  chorda  tympani,  the  submaxillary  ganglion, 
inferior  dental,  and  hypoglossal.  It  supplies  the 
mucous  membrane  of  the  mouth  and  tongue  (anterior 
two-thirds),    the    gums,    sublingual    gland,    and    the 


ANATOMY  AND  PHYSIOLOGY  OFTHE  BRAIN    375 

filiform  and  fungiform  papillae  in  the  mucous  mem- 
brane on  the  back  of  the  tongue. 

The  Sixth  Nerve. — The  sixth  or  abducens  has 
an  apparent  origin  in  the  groove  between  the  pons 
and  medulla.  It  runs  to  the  lower  and  outer  part 
of  the  dorsum  sellse,  and  traverses  the  floor  of  the 
cavernous  sinus  external  to  the  carotid  artery,  and, 
receiving  branches  from  the  cavernous  and  carotid 
plexuses,  enters  the  orbit  by  the  sphenoidal  fissure 


Frontal 


^uperiot  division  oj  oculo-mofor^ 

litferior  division  of  ocido-motor. 
Ihdncent. 
Ophthalmic  rein. 


Relations  of  structures  passing  through  the  sphenoidal  fissure.     (Gray.) 


between  the  two  heads  of  the  external  rectus;  it 
receives  a  branch  from  the  ophthalmic  nerve,  and 
supplies  the  above-named  muscles. 

The  Seventh  Nerve. — The  seventh  or  facial 
has  a  superficial  origin  from  the  depression  between 
the  olivary  and  restiform  bodies  of  the  medulla  oblon- 
gata. Between  it  and  the  eighth  is  the  pars  inter- 
media, which  joins  the  facial  in  the  auditory  canal. 
The  nerve  runs  outward  to  the  internal  meatus, 
where  it  runs  in  a  groove  on  the  auditory  nerve, 
enters  the  aqueductus  Fallopii,  and  emerges   at  the 


376 


THE  NERVE  SYSTEM 


Fia.  136 


Terminaiiona 
stipratrochle 

infratrochle( 
of  nasal. 


^^^m\\   ^ 


The  nerves  of  the  scalp,  face,  and  side  of  the  neck.     (Gray.) 


ANATOMY  AND   PHYSIOLOGY  OF  THE  BRAIN    377 

stylomastoid  foramen.  It  presents  within  the  aque- 
duct, near  the  hiatus  Fallopii,  a  reddish  enlargement, 
the  geniculate  ganglion.  Outside  the  cranium  it 
runs  forward  in  the  parotid  gland,  and  divides  behind 
the  ramus  into  the  cervicofacial  and  temporofacial 
divisions.  In  the  parotid  and  vicinity  the  radiating 
branches  form  the  pes  anserinus. 

The  facial  nerve  supplies  all  the  muscles  of  expres- 
sion of  the  face. 

The  Auditory  Nerve. — The  eighth  or  auditory 
is  the  special  nerve  of  the  sense  of  hearing.  Super- 
ficially it  appears  at  the  lower  border  of  the  pons, 
external  to  the  facial.  It  has  two  roots — one  from  the 
inner  side  of  and  one  from  the  front  of  the  restiform 
body.  It  runs  to  the  internal  auditory  meatus  with 
the  facial  nerve,  the  two  being  separated  by  the  pars 
intermedia  and  the  auditory  artery.  The  nerve  in 
the  meatus  divides  into  a  cochlear  and  a  vestibular 
branch,  whose  distributions  within  the  ear  are  described 
under  the  special  sense  of  hearing. 

The  Ninth  Nerve. — The  ninth  or  glossopharyngeal 
arises  superficially  by  several  filaments  from  the 
groove  between  the  olivary  and  restiform  bodies  at 
the  upper  part  of  the  medulla;  deeply  through  the 
lateral  tract  to  a  gray  nucleus  in  the  floor  of  the 
fourth  ventricle. 

The  nerve  runs  through  the  middle  part  of  the  jugular 
foramen  with  the  vagus  and  spinal  accessory,  in  a 
separate  sheath,  and  here  presents  two  successive 
ganglionic  enlargements,  the  jugular  and  the  petrous 
ganglia.  Outside  the  cranium  it  passes  between  the 
jugular  vein  and  the  internal  carotid  artery,  descending 
in  front  of  the  latter,  and  beneath  the  styloid  process 
and  its  muscles,  to  the  lower  border  of  the  stylo- 
pharyngeus,  and  supplies  the  mucous  membrane  of 
the  tongue.  It  then  crosses  this  muscle  and  divides 
into  branches  beneath  the  hyoglossus.    In  the  jugular 


378  THE  NERVE  SYSTEM 

foramen  it  grooves  the  lower  border  of  the  petrous 
portion  of  the  temporal  bone. 

The  Pneumogastric  Nerve. — The  tenth,  vagus, 
or  pneumogastric  is  both  motor  and  sensor.  Its 
apparent  origin  is  by  twelve  to  fifteen  filaments 
below,  and  in  the  line  of  the  origin  of  the  ninth;  its 
deep  origin  is  from  a  nucleus  in  the  lower  part  of  the 
fourth  ventricle.  It  passes  through  the  jugular  foramen 
in  the  same  sheath  with  the  spinal  accessory,  a  par- 
tition separating  them  from  the  ninth,  and  develops 
the  ganglion  of  the  root  of  the  vagus.  Emerging  from 
the  foramen,  it  forms  the  ganglion  of  the  trunk  of  the 
vagus. 

The  ganglio7i  of  the  root  (ganglion  jugulare)  is  gray 
in  color  and  spherical,  its  diameter  about  two  lines. 
It  has  branches  of  communication  with  the  accessory 
part  of  the  spinal  accessory,  w4th  the  petrous  ganglion 
of  the  ninth,  with  the  facial,  and  with  the  superior 
cervical  ganglion  of  the  sympathetic. 

The  ganglion  of  the  trunk  (ganglion  cervicale)  is 
larger,  of  a  reddish  color,  and  cylindrical  form.  Its 
surface  is  crossed  by  the  accessory  portion  of  the 
eleventh,  and  it  communicates  with  the  hypoglossal, 
the  upper  two  cervical,  and  the  sympathetic  nerves. 

The  vagus  then  descends  between  the  internal 
carotid  artery  and  the  jugular  vein  to  the  thyroid 
cartilage,  then  between  the  vein  and  the  common 
carotid  to  the  root  of  the  neck;  where  it  enters  the 
thorax  and  gives  off  branches  to  the  heart  (cardiac 
plexuses),  lungs  (pulmonary  plexuses),  and  esophagus; 
it  then  passes  through  the  esophageal  opening  in  the 
diaphragm  to  enter  the  abdominal  cavity  w^here  it 
gives  off  branches  to  the  solar  plexus,  the  stomach, 
liver,  spleen,  kidneys,  suprarenal  glands,  and  pan- 
creas. 

The  Eleventh  Pair. — The  eleventh,  or  spinal 
accessory,  consists  of  a  spinal  portion  and  an  accessory 


ANATOMY  AND  PHYSIOLOGY  OF  THE  BRAIN     379 

part  to  the  vagus.  The  latter  part  arises  as  five  or 
six  filaments  from  the  lateral  tract  of  the  medulla, 
below  the  origin  of  the  vagus. 

The  spinal  portion  arises  from  the  lateral  column 
of  the  cord  as  low  as  the  sixth  cervical  nerve,  the 
fibers  being  connected  with  the  anterior  horn  of  gray 
matter.  This  part  then  ascends,  between  the  posterior 
nerve  roots  and  the  ligamentum  denticulatum,  through 
the  foramen  magnum,  then  out  again  by  the  jugular 
foramen,  lying  in  the  sheath  of  the  vagus,  and  here 
communicates  with  the  accessory  portion.  After 
its  exit  from  the  skull  it  crosses  the  internal  jugular 
vein  and  pierces  the  sternomastoid  to  end  in  the 
trapezius  muscle. 

The  Hypoglossal. — The  twelfth,  or  hypoglossal, 
nerve  arises  by  ten  to  fifteen  filaments  from  the  groove 
between  the  pyramid  and  olivary  body  in  the  medulla. 
The  deep  origin  is  from  a  nucleus  in  the  floor  of  the 
fourth  ventricle.  The  filaments  form  two  bundles 
which  pierce  the  dura  separately  and  unite  in  the 
anterior  condylar  foramen.  The  nerve  descends  behind 
the  internal  carotid  artery  and  internal  jugular  vein, 
closely  bound  to  the  vagus. ^ 

The  Spinal  Nerves.— The  spinal  nerves  consist,  on  each 
side,  of  eight  cervical,  twelve  thoracic,  five  lumbar, 
five  sacral,  and  one  coccygeal,  in  all  thirty-one  pairs, 
which  arise  from  the  cord  by  two  roots,  anterior  and 
posterior.  The  latter  are  the  larger,  and  are  supplied 
with  ganglia.  The  suboccipital  or  first  cervical  nerve 
has  no  ganglion.  The  two  roots  unite  just  beyond 
the  ganglion,  and  the  resulting  trunk  divides  into  two 
divisions,  anterior  and  posterior,  each  containing 
fibers  from  both  roots,  sensor  and  motor.  The  posterior 
division  divides  into  an  external  and  an  internal  branch. 
The  anterior  divisions  in  the  dorsal  region  remain 
separate,    but    elsew^here    they    unite    into    plexuses. 

'  See  Fig.  131  for  origin  of  spinal  nerves. 


380  THE  NERVE  SYSTEM 

They  are  larger  than  the  posterior.  Each  division  is 
connected  with  the  sympathetic  gangha  along  the 
vertebral  column,  by  means  of  nerve  trunks  called 
rami  communicantes.  (See  Sympathetic  System,  p. 
385.) 

The  Cervical  Plexus. — The  cervical  plexus  is 
formed  by  the  anterior  divisions  of  the  upper  four 
cervical  nerves,  which  emerge  between  the  scalenus 
medius  and  rectus  anticus  major.  It  lies  upon  the 
scalenus  medius  and  levator  anguli  scapulae,  beneath 
the  sternomastoid.  Each  nerve  except  the  first 
divides  into  a  branch  for  the  nerve  above  and  one  for 
the  nerve  below.  The  anterior  division  of  the  first 
(suboccipital)  nerve  grooves  the  atlas  beneath  the 
vertebral  artery,  and  joins  the  second,  supplying  the 
rectus  lateralis  and  recti  antici  muscles.  It  commu- 
nicates with  the  sympathetic  vagus,  and  hypoglossal 
nerves. 

Its  branches  are  superficial  and  deep. 

The  superficial  are  divided  into  ascending  and 
descending. 

Ascending  Branches.  —  (a)  The  superficialis  colli, 
(6)  auricularis  magnus  (great  auricular),  (c)  occipital 
minor. 

Descending  Phrenic,  from  the  third,  fourth,  and 
fifth,  descends  on  the  scalenus  anticus,  then  between 
the  subclavian  artery  and  vein,  and  crosses  the  internal 
mammary  artery.  It  then  crosses  in  front  of  the  root 
of  the  lung  and  runs  between  the  pericardium  and 
mediastinal  pleura  to  the  diaphragm. 

The  Brachial  Plexus. — The  brachial  plexus  is 
formed  by  the  anterior  divisions  of  the  lower  four 
cervical  and  first  thoracic,  as  follows:  The  fifth  and 
sixth  form  an  upper;  the  seventh,  a  middle;  and  the 
eighth  cervical  with  first  dorsal  a  lower  trunk.  Each 
of  these  trunks  then  separates  into  an  anterior  and  a 
posterior  branch. 


ANATOMY  AND  PHYSIOLOGY  OF  THE  BRAIN    381 

The  anterior  branches  of  the  upper  and  middle 
trunks  form  the  outer  cord  of  the  plexus;  the  anterior 
branch  of  the  lower,  the  inner  cord;  of  the  posterior 
cord  it  is  variously  stated  that  the  posterior  branches  of 
all  three  trunks  form  it,  or  that  the  posterior  branches 
of  the  upper  and  middle  trunks  form  it,  while  the 

Fig.  136 


C.  with  Phrenic 

VII  C^vical 


Anterior  division 
o}  Middle  Ti-unk 


Anterior  division  of  Upper  Trunk 

External  Anterior  Thoracic 
Posterior  division  of  Upper  2'runk 
Upper  Sub-scapular 

Middle  and  Lower 
Sub-scapular 


Lower  Trunk 


Posterior  Thoracic 


Anterior  division  of  Lower  Trunk 
Posterior  division  of  Lower  Trunk 

Internal  Anterior  Thoracic 


Lesser  Internal  Cutaneous' 

Internal  Cutaneous' 


Musculo-cutaneous 


Ulnars 
Museulo-spiral'' 


Plan  of  the  brachial  plexus.     (Gray.) 


posterior  branch  of  the  lower  trunk  joins  the  musculo- 
spiral  nerve.    It  is  altogether  a  matter  of  dissection. 

The  plexus  is  at  first  between  the  anterior  and  middle 
scaleni,  then  above  and  external  to  the  subclavian 
artery.  It  passes  behind  the  clavicle  and  subclavius, 
lying  on  the  subscapularis  and  serratus  magnus  muscles. 
The  cords  lie  external  to  the  first  part  of  the  axillary 


382  THE  NERVE  SYSTEM 

artery,  but  on  three  sides  of  the  second  part  of  that 
vessel. 

The  branches  of  the  brachial  plexus  supply  the 
muscles  of  arm,  forearm,  fingers,  and  the  muscles 
of   the   chest. 

The  Lumbar  Plexus. — ^The  lumbar  plexus  is  formed 
in  the  substance  of  the  psoas  muscle,  in  the  following 
manner:  Each  of  the  first  four  lumbar  nerves  divides 
into  an  upper  and  a  lower  branch.  Just  before  dividing 
the  first  receives  the  twelfth  thoracic  nerve,  and  the 
third  and  fourth  send  each  a  branch  to  the  nerve  below. 

The  upper  branch  of  the  first  subdivides  into  the 
iliohypogastric  and  ilioinguinal  nerves.  The  lower 
branch  of  the  first  passes  downward  and  subdivides 
into  two  branches,  one  of  which  unites  with  the 
upper  branch  of  the  second  to  form  the  genitocrural 
nerve.  The  other  unites  with  the  lower  branch  of  the 
second  to  form  a  cord.  This  cord  passes  downward, 
and  gives  off  the  external  cutaneous  nerve  and  a  branch 
to  the  obturator,  after  which  it  unites  with  the  upper 
branches  of  the  third  and  fourth  to  form  the  anterior 
crural  nerve.  The  lower  branches  of  the  third  and 
fourth  unite  to  form  the  obturator  nerve. 

The  branches  derived  from  the  above  plexus  inner- 
vate the  skin  and  muscles  over  the  anterior  and 
internal  aspect  of  the  thigh,  leg,  instep,  and  external 
genital  organs. 

The  Sacral  Plexus. — The  sacral  plexus  is  formed 
by  the  anterior  divisions  of  the  first,  second,  third, 
and  part  of  the  fourth  sacral  nerves,  together  with  the 
lumbosacral  cord. 

The  lumbosacral  cord,  with  the  first,  second,  and 
part  of  the  third  sacral  nerve,  is  continued  into  the 
upper  great  branch  of  the  plexus,  and  the  remainder  of 
the  plexus  forms  the  lower  or  smaller  branch. 

The  branches  from  this  plexus  supply  the  muscles 
and  skin  over  the  buttocks,  back  of  thigh  and  leg, 
and  the  sole  of  the  foot. 


THE  SYMPATHETIC  NERVE  SYSTEM        383 


THE    SYMPATHETIC   NERVE   SYSTEM 

The  sympathetic  system  consists  of  numbers  of 
ganglia  connected  with  one  another  by  extension  of 
their  nerve  trunks.  It  is  not  an  independent  system 
for  the  conveyance  of  nerve  impulses,  but  is  in  rela- 
tion with  the  cerebrospinal  system  of  nerves  through 
communicating  branches. 

The  ganglia  are  classified  as  central  ganglia  w^hich 
are  arranged  on  either  side  of  the  spinal  column,  and 
are  connected  to  each  other  by  nerve  trunks,  forming 
the  gangliated  cord.  The  central  ganglia  extend  from 
the  base  of  the  skull  to  the  coccyx,  and  communicate 
with  the  spinal  nerves  by  means  of  nerves  called  rami 
communicantes. 

The  ganglia  of  the  cord  are  classified  for  purpose 
of  study  into  the  following  groups: 

Cervical  portion 3  pairs  of  ganglia. 

Thoracic  portion  10  to  12  pairs  of  ganglia. 

Lumbar  portion 4  pairs  of  ganglia. 

Sacral  portion 4  or    5  pairs  of  ganglia. 

The  ganglia  of  the  sympathetic  system  are  further 
arranged  into  minute  plexuses  called  the  three  great 
gangliated  plexuses.  They  are  situated  in  the  thoracic 
and  abdominal  cavities  and  receive  interconnecting 
nerve  trunks  which  form  the  following  plexuses:  (1) 
The  cardiac,  which  receives  nerve  trunks  from  the 
upper  three  cervical  ganglia,  and  gives  off  peripheral 
branches  to  the  heart,  lungs;  (2)  the  solar  or  celiac 
plexus,  which  receives  nerve  trunks  (splanchnic  nerves) 
from  the  thoracic  portion  and  gives  off  terminal 
branches  which  form  underlying  plexuses  and  inner- 
vate the  muscles  of  the  intestinal  wall,  and  other 
organs  of  the  abdominal  cavity,  bloodvessels,  and 
secreting  cells  of  glands;  (3)  the  hypogastric  plexus, 
which  receives  branches  from  the  lumbar  and  sacral 


384 


THE  NERVE  SYSTEM 


Superior  cervical  ganglion. 


Middle  cervical  ganglion. 

/ 
Jnjerior  cervieal  ganglion. 


Sacral  ganglia. 


Ganglion  tmpar 


Pharyngeal  branches 


Cardiac  branches. 


Deep  cardiac  plexus. 

Superficial  cardiac  plexus 


Solar  plexus. 


Aortic  plexus 


Hypogastric  plexus 


The  sympathetic  uerve  system. 


THE  SYMPATHETIC  NERVE  SYSTEM        385 

portion  of  the  cord  and  distributes  branches  to  the 
bladder,  rectum,  organs  of  reproduction,  etc. 

There  are  other  gangUa  situated  in  the  bony  cavities 
of  the  face  and  skull,  and  portions  of  the  neck  and 
face,  which,  on  the  one  hand,  are  in  intimate  relation 
with  the  cerebrospinal  system  through  branches  of 
communication  received  from  the  cranial  nerves,  and, 
on  the  other  hand,  .give  off  branches  of  distribution 
to  the  salivary  glands,  organs  of  special  sense,  particu- 

FiG.  138 


S  p 


INTERNAL  BRANCH 

EXTERNAL  BRANCH 


POSTERIOR  PRIMARY 
DIVISION 


NTERIOR  PRIMARY 
DIVISION 


RAMUS  COMMUNICANS 


Plan  of  the  constitution  of  a  spinal  nerve.     (W.  Keiller,  in  Gerrish's 
Text-book  of  Anatomy.) 


larly  nerves  from  the  ciliary  ganglion  which  controls 
the  regulation  of  the  pupil  in  regard  to  the  admission 
of  light  to  the  retina. 

The  Connections  of  the  Sympathetic  Ganglia  with 
the  Spinal  Nerves. — The  spinal  nerves  as  they  leave 
the  foramen  between  the  vertebra  are  connected  to 
the  ganglia  by  two  small  nerves  called  the  rami  com- 
municantes.  One  branch  is  white,  the  other  gray. 
The  white  rami  are  found  connecting  only  the  spinal 
nerves  included  between  the  first  thoracic  nerve  and 
the  second  or  third  lumbar  and  the  corresponding 
ganglia.  The  gray  rami  are  found  passing  from  each 
one  of  the  ganglia  to  the  corresponding  spinal  nerve. 
25 


386  THE  NERVE  SYSTEM 

The  White  Rami. — These  contain  medullated  nerve 
fibers  and  have  their  origin  in  the  ganglia  of  the  cord; 
and  other  axones  also  pass  from  the  ganglia  forward 
by  way  of  the  rami  to  the  spinal  nerve,  and  terminate 
through  these  nerves,  to  be  distributed  to  the  plexuses 
in  the  abdominal  and  thoracic  organs. 

The  Gray  Rami. — These  are  composed  of  non- 
medullated  nerve  fibers;  the  axones  arise  in  the  nerve 
cells  of  the  central  ganglia  and  pass  to  the  spinal 
nerve,  wherein  they  are  conveyed  to  the  structure 
in  the  skin,  non-striated  muscles  of  bloodvessels  and 
the  hair  foUicles,  also  the  epithelial  cells  of  the  glands. 
The  foregoing  description  of  the  white  and  gray  rami 
show  the  course  of  the  efferent  nerves  from  the  nerve- 
cells  situated  in  the  lateral  and  anterior  portion  of 
the  gray  matter  in  the  thoracic  and  lumbar  regions 
of  the  spinal  cord.  The  axones  from  these  nerve  cells 
leave  the  spinal  cord  by  way  of  the  anterior  root, 
at  the  point  where  the  anterior  and  posterior  roots 
join  to  form  the  common  trunk  of  the  spinal  nerve, 
to  pass  to  the  ganglion  wherein  the  axones  are  in 
relation  with  other  neurones. 

The  afferent  sympathetic  fibers  give  rise  to  pain 
and  other  reflex  phenomena  when  stimulated.  They 
reach  the  spinal  centres  by  passing  through  the  gray 
rami  to  the  ganglion  on  the  posterior  root,  where 
they  communicate  with  other  neurones  and  are  con- 
veyed by  their  axones  to  the  cells  in  the  posterior 
horns  of  the  spinal  cord;  some  fibers  pass  into  and 
through  the  white  rami. 

The  Functions  of  the  Sympathetic  System. — It  is  a 
connecting  link  between  the  cerebrospinal  system  and 
the  tissues  of  the  body  w^hich  carry  on  the  involun- 
tary functions.  By  the  connection  of  the  ganglion 
with  each  other,  and  the  spinal  cord  and  brain  at 
different  levels,  through  the  rami  communicantes, 
one  can  easily  understand  the  numbers  of  different 
routes  by  which  impulses  can  pass,  thus  influencing 


QUESTIONS  387 

several  different  structures  by  reflex  actions  taking 
place  between  these  groups  of  ganglia  and  their  asso- 
ciated neurones.  The  sympathetic  nerves  convey 
nerve  impulses  which,  in  response  to  stimuli  trans- 
mitted to  them  through  ganglia  and  their  connections 
with  the  cerebrospinal  system,  control  the  secretion 
of  the  glands;  others  control  the  caliber  of  the  blood- 
vessels by  vasoconstrictor  and  vasodilator  nerves, 
passing  to  the  muscular  coat -of  the  vessel,  the  former 
regulating  the  contraction,  the  latter  the  dilatation 
of  the  bloodvessels;  others  regulate  the  force  and 
rate  of  the  heart  muscle — called  cardio-accelerator, 
which  increase  the  action,  and  cardio-inhibitor,  w^hich 
decrease  it.  Other  nerves  convey  impulses  to  the 
organs  of  special  sense,  as  those  regulating  the  size 
of  the  pupil.  Emotional  states,  either  of  an  exciting 
or  depressing  nature,  influence  the  activity  of  the 
sympathetic  system  by  impulses  transmitted  through 
the  spinal  cord  and  ganglia  from  the  brain,  which 
reach  the  organs  of  digestion,  etc.,  by  reflex  pathways 
established  between  the  ganglia  and  ganglionic  plexuses 
and  their  secreting  cells  and  bloodvessels. 


QUESTIONS 

1.  Give  the  divisions  of  the  nerve  system. 

2.  What   parts   of   the    nerve   system    are   included    under    the 
cerebrospinal  system? 

3.  What  is  the  essential  cell  structure  of  all  nerve  energy  and 
reflex  called? 

4.  Name  the  protoplasmic  processes  given  off  from  a  neurone. 

5.  How  large  are  the  bodies  of  nerve  cells? 

6.  Give  the  classification  of  neurones  as  regards  their  number 
of  processes. 

7.  Describe   a   dendrite   of  a   neurone.      Do   they   increase   the 
functionating  surface  of  a  neurone? 

8.  What  is  the  function  of  the  dendrites  as  regards  nerve  impulses? 

9.  Describe  an  axone  or  axis-cylinder. 

10.  How  long  is  an  axone? 

11.  How  many   axones   are   given   off   from   a   neurone?      Name 
them  as  to  the  numbers. 

12.  What  do  you  understand  by  tolendria? 


388  THE  NERVE  SYSTEM 


13.  What  is  the  function  of  the  axones  as  regards  nerve  impulses? 

14.  What  do  nerve  fibres  consist  of?    Name  the  two  varieties. 

15.  Name  the  portions  of  a  meduUated  nerve  fiber. 

16.  Differentiate  a  medullated  from  a  non-medullated  nerve 
fiber. 

17.  What  do  you  understand  by  a  node  of  Ranvier? 

18.  What  is  the  difference  in  color  between  nerve  tissue  formed 
of  medullated  and  non-medullated  nerve  fibers? 

19.  What  forms  a  nerve?  What  are  the  functions  of  the  epi- 
neurium,  perineurium,  endoneurium? 

20.  Name  the  two  kinds  of  nerve  tissue  which  support  the  nerve 
cells.    Are  they  active  as  regards  the  conveyance  of  nerve  impulses? 

21.  What  do  you  understand  by  the  superficial  and  deep  origin 
of  a  nerve? 

22.  How  does  an  efferent  nerve  end? 

23.  How  does  an  afferent  nerve  end? 

24.  Name  some  of  the  end-organs. 

25.  Does  an  efferent  nerve  convey  impulses  from  the  brain  and 
spinal  cord  to  the  tissues? 

26.  In  which  direction  does  an  afferent  nerve  convey  impulses? 

27.  How  does  an  efferent  nerve  end  in  a  skeletal  muscle? 

28.  Describe  a  nerve  plexus. 

29.  Do  the  nerve  fibers  in  a  plexus  maintain  the  same  function 
as  the  nerve  possesses  from  its  origin? 

30.  Where  are  ganglia  found?  Do  their  neurones  connect  with 
the  brain  and  spinal  cord? 

31.  What  is  the  function  of  a  ganglia  as  regards  the  conveyance 
of  nerve  impulses? 

32.  Name  the  two  classifications  of  nerves  concerned  in  all  nerve 
action  or  reflex. 

33.  Describe  the  physiology  of  a  nerve. 

34.  What  do  you  understand  by  the  term  nerve  irritability? 
Excitability? 

35.  What  is  essential  to  develop  or  convey  nerve  impulses  in  a 
nerve? 

36.  Name  some  special  stimuli  which  develop  impulses  in  the 
endings  of  afferent  neurones  and  are  conveyed  to  the  brain  and 
spinal  cord. 

37.  How  do  stimuli  arise  which  develop  impulses  in  the  neurones 
of  efferent  nerves  and  are  conveyed  to  muscles,  organs,  etc.? 

38.  Name  the  parts  of  the  nerve  system  included  under  the 
central  nerve  system. 

39.  Where  is  the  spinal  cord  located  in  the  body?  How  long  is  it? 
What  is  its  weight? 

40.  Name  the  membranes  surrounding  the  spinal  cord. 

41.  Name  the  chief  columns  of  the  spinal  cord.  What  composes 
them?    Give  their  general  function. 

42.  Give  a  brief  description  of  a  cross-section  of  the  spinal  cord. 

43.  What  is  the  function  of  the  efferent  motor  nerve  cells  in  the 
spinal  cord?    Afferent  sensor  nerve  cells?    Intrinsic  nerve  cells? 

44.  How  many  pairs  of  spinal  nerves  are  there?  Give  the  number 
as  to  the  portion  of  the  cord  from  which  they  arise. 


QUESTIONS  389 

45.  Define  a  reflex  action. 

46.  What  do  you  understand  by  sensor  conduction  as  regards  the 
nerve  fibers  in  the  spinal  cord?    Motor  conduction? 

47.  Name  the  membranes  of  the  brain. 

48.  What  parts  of  the  central  nerve  system  are  included  under 
the  brain? 

49.  What  are  the  functions  of  the  medulla  oblongata?  The  pons 
Varolii? 

50.  What  is  the  membrane  called  which  separates  the  cerebrum 
from  the  cerebellum? 

51.  What  is  the  functi(5n  of  the  cerebellum? 

52.  How  much  does  the  cerebelluni  weigh? 

53.  Name  the  lobes  of  the  cerebrum. 

54.  What  structure  connects  the  two  lateral  halves  of  the  brain? 

55.  Name  the  ventricles  of  the  brain. 

56.  Give  a  brief  description  of  the  structure  of  the  cerebrum. 

57.  What  is  the  weight  of  the  brain  in  the  adult  male?    Female? 

58.  Where  is  the  motor  area  located  upon  the,  surface  of  the 
cerebrum?    Sensor? 

59.  What  parts  of  the  body  are  controlled  from  the  nerve  cells 
in  the  motor  area? 

60.  Does  the  motor  area  control  the  limbs  of  the  -same  side  of 
the  body  upon  which  it  is  located? 

61.  What  are  the  functions  of  peripheral  nerves? 

62.  Name  the  cranial  nerves. 

63.  Name  the  nerves  of  smell,  sight,  taste,  and  hearing. 

64.  What  nerve  supplies  all  the  muscles  of  expression  of  the  face? 

65.  What  nerve  supplies  the  heart,  lungs,  through  the  cardiac 
and  pulmonary  plexuses  respectively?  The  liver,  stomach,  spleen, 
kidneys? 

66.  What  nerve  tissue  comprises  the  sympathetic  system?  Is  it 
an  independent  system? 

67.  What  do  you  understand  by  the  gangliated  cord?  Is  it  an 
independent  system? 

68.  Name  the  groups  of  ganglia  of  the  cord. 

69.  What  are  the  nerves  called  which  connect  the  spinal  nerves 
with  the  sympathetic  ganglia? 

70.  Differentiate  the  nerve  fibers  in  a  gray  rami  from  a  white 
rami  communicantes. 

71.  Give  a  brief  description  of  the  functions  of  the  sympathetic 
system. 


CHAPTER  XVIII 
THE  ORGANS  OF  SPECIAL  SENSE 

The  nerve  system  is  the  means  by  which  the  indi- 
vidual is  brought  into  conscious  relation  with  the 
external  world.  This  consciousness  is  excited  by 
numerous  material  impressions  which  develop  nerve 
impulses  in  the  end-organs  of  the  skin,  the  tongue, 
nose,  eye,  and  ear,  and  are  conveyed  by  afferent 
nerves  to  the  centres  in  the  cortex  of  the  brain  where 
they  awake  sensations. 

These  sensations  vary  in  character.  Thus  one  may 
feel  happy,  fatigued,  hungry,  thirsty,  etc.,  as  a  result 
of  material  changes  going  on  within  the  body.  These 
are  usually  spoken  of  as  common  or  ordinary  sensa- 
tions. The  important  or  special  sensations  arise  as 
a  result  of  the  definite  impressions  made  upon  the 
highly  sensitive  end-organs,  as  touch,  pain,  tempera- 
ture, pressure,  taste,  smell,  light  and  its  varying 
qualities,  sound  and  its  varying  qualities.  The  physio- 
logic mechanisms  underlying  these  special  sensations 
are  spoken  of  as  tactile,  touch;  temperature,  pain, 
gustatory,  taste;  olfactory,  smell;  optic,  sight;  auditory, 
hearing,  and  are  known  as  the  special  senses. 

The  factors  necessary  to  the  production  of  the 
sensations  are:  (1)  A  special  physical  stimulus;  (2)  a 
specialized  terminal  organ  (end-organ) ;  (3)  an  afferent 
pathway  which  conveys  the  impulse  to  the  centres 
in  the  cortex  of  the  brain;  (4)  a  specialized  receptive 
sensor  cell  in  the  cortex  of  the  brain. 

The  special  senses  are  five  in  number:  sense  of 
touch,  sense  of  smell,  sense  of  sight,  sense  of  hearing, 
and  sense  of  taste. 


THE  SENSE  OF  TOUCH  391 


THE    SENSE    OF    TOUCH 


The  structures  essential  to  the  appreciation  of  the 
sense  of  touch  are  the  skin  and  mucous  membrane 
of  the  mouth,  etc.,  the  end-organs  therein  and  the 
afferent  nerves  which  convey  the  nerve  impulses  by 
pathways  through  the  cord  and  brain  to  the  cells  in 
the  tactile  area  of  the  cerebrum  which  are  located  in 
the  parietal  lobes. 

The  end-organs  are  the  highly  specialized  organs 
found  not  only  in  the  skin,  but  in  other  sense  organs. 
They  are  the  sensitive  bodies  intervening  between 
the  surface  coming  in  contact  with  the  skin,  etc.,  and 
the  terminal  filaments  of  afferent  nerves.  They  are 
more  sensitive  than  the  terminals  of  afferent  nerves 
and  receive  specific  stimuli  which  excite  them  to 
activity;  and  they  in  turn  transmit  the  impulses  to 
the  aft'erent  nerves.  However,  these  end-organs  are 
usually  spoken  of  as  the  terminations  of  afferent 
nerves. 

Classification  of  End-organs. — (1)  Free  Endings.^ 
Club-shaped  processes  found  in  and  among  the  cells  of 
the  epidermis  (upper  layer  of  skin) ;  they  are  termina- 
tions of  minute  fibers  of  afferent  nerves. 

2.  Tactile  Cells. — ^They  are  oval,  nucleated  bodies 
found  in  the  deep  layer  of  the  epidermis.  They  are 
embraced  by  a  crescentic-shaped  body  (tactile  disk) 
which  is  directly  connected  with  the  afferent  nerve. 

3.  The  Corpuscles  of  Meissner  and  Wagner. — These 
are  found  in  the  papillae  of  the  derma  (deep  layer  of 
skin),  especially  in  the  palm  of  the  hand  and  finger 
tips.  They  are  bodies  which  consist  of  numbers  of 
tactile  disks  surrounded  by  connective  tissue  and  are 
in  connection  with  the  terminals  of  afferent  nerves. 

4.  Hair  Wreaths. — ^They  are  minute  nerve  fibers, 
consisting  of  a  whole  axis-cylinder,  which  surround 
the  hair  follicle  just  beneath  the  opening  of  the  seba- 


392     THE  ORGANS  OF  SPECIAL  SENSE 

ceous  glands.  They  are  arranged  in  the  form  of  a 
wreath. 

5.  Corpuscles  of  Vater  or  Pacini. — They  are  oval- 
shaped  structures  situated  along  the  course  of  afferent 
nerves  distributed  to  the  skin  on  the  palms  of  the 
hands  and  soles  of  the  feet,  external  genital  organs, 
joints,  etc.  They  consist,  when  examined  under 
the  microscope,  of  bulbs  composed  of  granular  pro- 
toplasm surrounded  by  layers  of  connective  tissue, 
and  are  joined  by  the  axis-cylinder  of  the  afferent 
nerve. 

The  sense  of  touch  is  the  sensation  conveyed  to 
the  brain  by  an  object  we  touch  coming  in  contact 
with  the  end-organs  in  the  skin  and  mucous  mem- 
branes. By  this  sense  we  are  enabled  to  touch  and 
be  touched  by  objects  and  determine  their  size 
and  weight;  quality,  whether  hard  or  soft,  rough 
or  smooth,  sharp  or  dull,  etc.;  also  the  temperature 
of  a  body  or  surface  coming  in  contact  with  the 
skin  and  mucous  membranes,  whether  it  is  hot  or 
cold. 

The  Skin. — The  skin  possesses  (1)  touch  sense  and 
(2)  temperature  sense.  The  touch  sense  is  subdivided 
into  (a)  pressure  sense  and  (6)  place  sense. 

The  touch  sense  is  stimulated  by  mechanical  pressure 
coming  in  contact  with  the  end-organs  in  the  skin 
and  mucous  membrane. 

Touch  Spots. — The  areas  of  the  skin  and  membrane, 
which  when  stimulated  by  an  object,  as  pin,  knife, 
etc.,  give  rise  to  the  sensation  of  touch,  are  not 
general  throughout  the  surface  of  the  skin,  but  are 
localized  spots  in  the  skin  (these  areas  are  called 
touch  spots)  with  intervals  which  are  insensitive  to 
stimuli. 

The  greater  number  of  touch  spots  in  a  given  area 
the  greater  is  the  acuteness  of  the  touch.  These  spots 
are  more  numerous  in  the  hands  and  in  the  neighbor- 
hood of  hair  follicles.     The  skin  of  the  index  finger 


THE  SENSE  OF  TOUCH  393 

over  the  last  phalanx  is  particularly  well  supplied 
with  touch  spots  localized  in  the  corpuscles  of  Meissner, 
thus  rendering  the  tip  of  the  finger  more  acute  in  the 
sense  of  touch.  It  must  be  remembered  that  when 
the  pressure  and  temperature  (extremes  of  heat  or 
cold)  of  an  object  are  too  severe  the  sense  of  touch 
and  temperature  is  lost  in  the  sense  of  pain.  The 
sense  of  touch  is  replaced  by  the  sense  of  pain  when 
the  skin  is  bruised  or  burned,  so  that  the  epidermis 
is  destroyed,  leaving  the  nerves  too  exposed. 

The  sense  of  pressure  is  the  variety  of  the  touch 
sense  which  is  based  on  the  fact  that,  when  pressure  is 
brought  to  bear  along  with  touching  an  object,  the 
pressure  of  the  object  coming  in  contact  with  the  skin 
must  reach  a  certain  intensity  before  the  sensation  of 
weight  will  be  appreciated,  and  permit  the  individual 
to  determine  the  amount  of  the  pressure,  and  gauge 
the  comparative  pressure  of  low  weights. 

The  Sense  of  Place. — Is, based  on  the  fact  that  when 
a  stimulus  touches  any  portion  of  the  skin  the  sensa- 
tion caused  thereby  is,  under  normal  conditions, 
always  referred  to  the  place  stimulated.  This  is 
always  the  case,  whether  the  place  of  stimulation  is 
at  two  points  near  or  distant  from  each  other  on  the 
same  side  of  the  body,  or  the  corresponding  place 
on  the  opposite  side.  These  areas  for  the  localization 
of  sensations  are  usually  arranged  in  circles  throughout 
the  surface  of  the  skin. 

The  Temperature  Sense. — This  is  supposed  to  be 
due  to  the  presence  in  the  skin  of  special  nerve-endings 
which  give  rise  to  sensations  of  heat  and  cold,  and 
are  different  from  each  other,  as  well  as  from  those 
end-organs  which  give  rise  to  sensations  of  touch. 
It  has  been  proved  by  investigation  that  throughout 
the  surface  of  the  skin  there  are  spots,  called  heat  and 
cold  spots,  which  if  stimulated  give  rise  to  sensations 
of  heat  and  cold.  Each  spot  responds  to  only  one 
kind  of  stimulus,  thus  a  warm  object  applied  to  the 


394     THE  ORGANS  OF  SPECIAL  SENSE 

skin  will  only  affect  the  heat  spots,  and  give  rise  to 
the  sensation  of  warmth,  and  the  application  of  a 
cold  one  will  only  influence  the  cold  spots  and  create 
a  sensation  of  coldness.  The  specific  physiologic 
stimuli  to  the  end-organs  controlling  the  temperature 
sense  are  termed  thermic  vibrations. 

The  muscle  sense  is  a  series  of  specific  sensations 
arising  as  a  result  of  the  activities  of  the  muscles 
of  the  body  or  its  individual  parts  of  which  we  are 
conscious.  They  are  called  muscle  sensations  and 
are  evoked  in  response  to  nerve  impulses  developed  in 
the  end-organs  in  the  muscles  and  tendons,  and  con- 
veyed by  afferent  nerves  and  their  connections  with 
nerve  cells  in  the  brain. 

By  the  consciousness  of  these  sensations  we  are 
able  to  perceive  (1)  the  duration  and  direction  of 
both  passive  and  active  movements  of  the  body;  (2) 
to  perceive  the  resistance  offered  to  movements  by 
external  bodies;  (3)  and  to  perceive  the  posture  of 
the  body  or  its  individual  parts. 


THE    ANATOMY    AND   PHYSIOLOGY   OF   THE 

STRUCTURES    CONCERNED   IN    THE 

SENSE    OF    SMELL 

The  structures  essential  to  the  sense  of  smell  are 
the  nasal  fossae,  the  olfactory  nerve  filaments  lying 
within  the  mucous  membrane,  and  the  olfactory 
tracts  which  are  collections  of  nerve  fibers  formed 
into  large  nerve  trunks  and  the  latter  ending  in  the 
nerve  cells  in  the  uncinate  convolutions  of  the  cere- 
brum (area  of  sense  of  smell).  Matter  in  the  gaseous 
or  volatile  state  is  the  means  whereby  the  peripheral 
nerves  are  stimulated,  in  which  are  developed  nerve 
impulses,  transmitted  to  the  cortex,  where  they  give 
rise  to  sensations  of  odor. 


THE  SENSE  OF  SMELL 


395 


The  Nasal  FossaB  or  Cavities. — These  are  two 
bony  cavities  separated  by  a  vertical  wall,  formed  by 
the  perpendicular  plate  of  the  ethmoid,  the  vomer, 
and  the  triangular  cartilage.  The  bony  walls  are 
lined   with   mucous   membrane.     On  the   outer   wall 


Fig.  139 


PROBE    P4g 
SINUS  THff^^^i 


OPENINGS   OF    POSTERIOR 
ETHMOIDAL  CELLS 


SPHENOIDAL 
SINUS 


External  wall  of  right  nasal  fossa,  parts  of  the  turbinates  having  been 
cut  away  to  show  the  orifices  of  the  sinuses  which  open  into  the  meatuses. 
(Testut.) 


each  cavity  communicates  by  means  of  foramen  and 
fissures  with  the  sphenoid,  frontal  sinuses,  the  antrum 
of  Highmore,  and  ethmoid  cells,  and  receives  on 
its    floor    the    opening    of    the    tear-duct    from    the 


396     THE  ORGANS  OF  SPECIAL  SENSE 

lacrymal  sac  in  the  inner  angle  of  the  eye.  By  means 
of  this  duct  the  tears  pass  from  the  conjunctiva  to 
the  nasal  cavity.  The  mucous  membrane  lining  the 
walls  of  the  nasal  fossse  is  divided  into  an  olfactory 
and  respiratory  portion;  in  the  former  the  mucous 
membrane  covers  the  superior  turbinated  bone  and 
upper  part  of  the  septum;  it  consists  of  a  neuro- 
epithelium;  the  respiratory  portion  is  the  term  given 
to  the  remaining  portion  of  the  membrane  cover- 
ing the  fossa.  The  membrane  lining  the  nasal  cavi- 
ties is  continued  through  the  foramen  and  fissures 
leading  from  it  into  the  sphenoidal  and  ethmoidal 
cells,  frontal  sinuses,  antrum  of  Highmore,  and 
pharynx. 

The  entrance  to  the  nasal  cavities  is  called  the 
anterior  nares;  the  back  of  the  nasal  cavities  open 
into  the  pharynx  and  is  called  the  posterior  nares  or 
choanse. 

The  End-organs. — ^The  end-organs  which  receive 
the  stimuli  that  give  rise  to  sensations  of  odor  consist 
of  olfactory  and  sustentacular  cells  which  rest  upon  a 
basement  membrane,  making  up  the  olfactory  portion 
of  the  mucous  membrane. 

Olfactory  sensations  are  classified  into  agreeable 
and  disagreeable,  depending  upon  the  sensations  they 
create  in  the  individual. 


THE    ANATOMY    AND    PHYSIOLOGY   OF    THE 

STRUCTURES    CONCERNED   IN  THE 

SENSE   OF    SIGHT 

The  Eye. — The  eye-ball  lies  in  the  fat  of  the  orbit, 
surrounded  by  a  tunic  of  fascia,  the  capsule  of  Tenon. 
It  is  composed  of  segments  of  two  spheres,  an  anterior 
smaller  and  a  posterior  larger,  the  junction  of  the 
sclerotic  and  cornea  indicating  their  limits.  It  measures 
one  inch  transversely  and  vertically,  and  somewhat  less 


THE  SENSE  OF  SIGHT  397 

from  before  backward.  Behind  it  receives  the  optic 
nerve  (the  nerve  of  the  sense  of  sight),  and  in  front 
are  the  eyeUds,  eyebrows,  etc.,  which  comprise  the 
so-called  appendages  of  the  eye. 

The  Appendages  of  the  Eye. — ^These  include  the 
eyebrows,  eyelids,  conjunctiva,  the  lacrymal  gland 
and  sac,  and  the  nasal  duct.  The  last  three  belong 
to  the  "lacrymal  apparatus." 

The  eyebrows  (supercilia)  are  two  prominent  tracts 
of  skin  above  the  orbit,  covered  by  thick  hairs.  They 
are  connected  with  the  orbicularis,  palpebrarum  cor- 
rugator  supercilii,  and  occipitofrontalis  muscles.  « 

The  lids  (palpebrse)  protect  the  eyeball.  Each  is 
composed  of  thin  skin,  areolar  tissue,  muscular  fibers, 
the  tarsal  cartilage  and  ligament.  Meibomian  glands, 
and  conjunctiva;  the  upper  lid,  which  is  also  the  more 
movable,  contains,  in  addition,  the  aponeurosis  of  the 
levator  palpebrse  muscle. 

The  lids  are  separated,  when  opened,  by  a 
space,  the  fissura  palpebrarum,  and  are  united  at  the 
angles  (canthi).  The  outer  angle  is  sharp,  and  the 
inner  is  more  obtuse.  At  the  inner  angle  on  each 
lid  is  found  the  lacrymal  tubercle,  pierced  by  the 
punctum  lacrymale,  the  upper  opening  of  the  lacrymal 
canal. 

The  tarsal  cartilages  (tarsi)  are  two  plates  of  dense 
fibrous  tissue,  one  in  each  lid. 

The  tendo  oculi  or  palpebrarum  is  Y-shaped.  The 
stem  is  attached  to  the  nasal  process  of  the  superior 
maxilla,  and  each  arm  to  one  of  the  tarsal  cartilages. 

The  palpebral  ligament  is  a  fibrous  membrane 
attached  to  the  tarsal  cartilages  and  to  the  correspond- 
ing margin  of  the  orbit. 

The  Meihoviian  glands  (sebaceous)  lie  on  the  inner 
surface  of  the  lids,  between  the  tarsal  cartilages  and 
the  mucous  membrane.  In  the  upper  lid  there  are 
about  thirty;  in  the  lower,  fewer. 


398     THE  ORGANS  OF  SPECIAL  SENSE 

The  lashes  (cilia)  are  short,  thick  hairs  forming  a 
double  row  on  the  free  margin  of  each  lid.  Above 
they  are  longer  and  more  numerous.  They  protect 
the  eyes  from  dust,  etc. 

The  conjunctiva  is  the  mucous  membrane  of  the 
eye.  The  palpebral  portion  is  very  thick  and  vascular, 
and  forms  at  the  inner  canthus  a  fold  known  as  the 
plica  semilunaris.  The  ocular  portion  is  loosely 
connected  to  the  sclerotic  coat,  but  over  the  cornea 
consists  only  of  the  conjunctival  epithelium. 

The  Lacrymal  Apparatus. — This  includes  the  gland, 
the  two  canals,  the  sac,  and  the  nasal  duct. 

The  gland  is  about  the  size  and  shape  of  a  small 
almond,  and  lies  in  a  depression  in  the  orbital  plate 
of  the  frontal  bone  just  inside  the  external  angular 
process.  Its  ducts,  ten  or  more  in  number,  run  beneath 
the  conjunctiva  and  open  separately  at  the  outer  part 
of  the  fornix. 

The  lacrymal  canals  commence  by  small  orifices, 
the  puncta,  on  the  margin  of  each  lid,  and  empty 
close  together  into  the  sac. 

The  lacrymal  sac  is  the  upper  dilated  part  of  the 
nasal  duct,  and  lies  in  a  depression  formed  by  the 
lacrymal  and  superior  maxillary  bones.  (See  Fig.  140, 
page  399.) 

The  nasal  duct  is  contained  in  a  canal  formed  by 
the  superior  maxilla,  lacrymal,  and  inferior  turbinated 
bones,  and  runs  from  the  lacrymal  sac  to  the  inferior 
meatus,  beneath  the  inferior  turbinate  bone  in  the 
nasal  cavity.  It  is  lined  by  a  mucous  membrane 
continuous  with  the  conjunctiva. 

The  secretion  from  the  lacrymal  glands  is  a  clear 
fluid  termed  the  tears,  which  is  secreted  by  cells  of 
the  gland  due  to  sensor  nerve  fibers  from  the  fifth 
nerve,  sending  out  impulses  in  response  to  reflex 
stimuli,  irritating  the  afterent  nerves  in  the  con- 
junctiva, as  foreign   bodies  in   the  eye,  etc.;  also   by 


THE  SENSE  OF  SIGHT 


399 


sympathetic  impulses  conveyed  to  the  secreting  cells 
by  way  of  the  sympathetic  filaments  from  the  sym- 
pathetic system  in  response  to  emotional  states  from 
the  brain  centres.  The  tears  consist  of  water  and 
inorganic  salts.  The  secretion  leaves  the  gland  by 
way  of  seven  or  eight  ducts  and  bathes  the  corneal 
surface  of  the  eye  during  the  act  of  winking,  thus 
moistening  the  eye  and  removing  foreign  bodies. 
It  then  passes  into  the  lacrymal  duct  to  drain  into  the 

Fig.   140 


The  lacrymal  apparatus.     (Gray.) 


nasal  cavity.  An  excess  secretion,  as  is  observed  in 
weeping,  or  due  to  a  foreign  body  in  the  conjunctiva, 
passes  over  the  lower  lid  and  drains  down  the  cheek, 
as  well  as  the  nasal  cavity. 

The  Eye-ball.—  This  consists  of  three  coats  enclosing 
the  refractive  media  or  humors.  They  are  the  sclerotic 
and  cornea  outside,  the  retina  internally,  and  the 
choroid  between  the  sclerotic  and  retina. 

The  sclerotic  coat  is  a  dense  fibrous  membrane,  white 


400     THE  ORGANS  OF  SPECIAL  SENSE 

and  smooth  externally,  excepting  where  it  receives 
the  insertion  of  the  recti  and  obliqui  muscles.  It 
covers  the  posterior  five-sixths  of  the  eye-ball.  Behind 
it  receives  the  optic  nerve  at  a  point  just  internal  to 
the  centre,  the  fibrous  sheath  of  the  former  being 
continuous  with  the  sclerotic. 

The  cornea  forms  the  anterior  sixth  of  the  external 
coat.  It  is  transparent  and  projecting,  and  nearly 
an  arc  of  a  true  sphere,  the  anterior  surface  being 
convex  and  the  posterior  surface  concave. 

The  choroid  or  intermediate  coat  is  continued  into  the 
cornea.  It  is  a  chocolate-colored,  vascular  structure 
lying  between  the  sclerotic  and  retina  and  investing 
the  posterior  five-sixths  of  the  eye-ball,  blending  in  front 
with  the  iris  after  forming  a  number  of  folds,  the 
ciliary  processes. 

The  ciliary  muscle  is  a  circular  plane  of  unstriped 
muscle  placed  between  the  choroid  and  sclerotic  at 
its  anterior  part.  It  consists  of  circular  and  radiating 
fibers.  This  muscle  aids  in  contracting  and  dilating 
the  size  of  the  pupil  in  response  to  nerve  stimuli,  and 
under  normal  conditions  regulates  the  amount  of 
light  entering  the  chamber  of  the  eye. 

The  iris  gives  to  the  eye  its  color  (depending  on 
the  pigment  present) .  It  is  a  thin,  contractile,  circu- 
lar membrane  presenting,  at  about  its  centre,  a  cir- 
cular aperture,  the  pupil.  It  is  suspended  in  the 
aqueous  humor  behind  the  cornea  and  in  front  of 
the  lens. 

The  arteries  are  supplied  from  the  long  and  anterior 
ciliary.  The  nerves  are  branches  of  the  lenticular 
ganglion  and  the  long  ciliary  from  the  nasal  branch 
of  the  ophthalmic.  They  form  a  plexus  around  the 
circumference  of  the  iris,  and  end  in  the  muscular 
fibers  and  in  a  network  on  the  front  of  the  iris.  The 
nerves  to  the  circular  fibers  come  from  the  motor 
oculi;  those  to  the  radiating,  from  the  sympa- 
thetic. 


THE  SENSE  OF  SIGHT  401 

The  Vitreous  Humor. — It  is  a  transparent,  gelatinous 
fluid  enclosed  in  a  transparent  membrane,  the  hyaloid, 
and  fills  about  four-fifths  of  the  eye-ball.  In  front 
it  is  hollowed  out  to  receive  the  lens  and  its  capsule, 
being  adherent  to  the  back  of  the  latter.  (See  Fig. 
141,  page  402.) 

The  Crystalline  Lens. — This  is  a  solid,  transparent, 
biconvex  body  which  lies,  enclosed  in  its  capsule,  in 
front  of  the  vitreous  and  behind  the  iris.  The  greater 
convexity  is  behind. 

The  capsule  is  an  elastic,  transparent,  structureless 
membrane,  in  contact  anteriorly  with  the  iris  and 
held  in  place  by  the  suspensory  ligament. 

The  suspensory  ligament  is  a  thin,  transparent 
membrane  placed  between  the  vitreous  humor  and 
the  ciliary  processes,  and  presents  externally  a  number 
of  folds  which  receive  those  of  the  ciliary  processes. 

The  Aqueous  Humor. — This  is  the  fluid  which  fills 
the  space  between  the  suspensory  ligament  and  cap- 
sule behind  and  the  cornea  in  front.  That  part  of  this 
space  which  lies  in  front  of  the  iris  is  called  the  anterior 
chamber;  the  part  behind  the  iris  is  the  posterior 
chamber.  The  latter  is  really  only  the  small  interval 
between  the  iris,  suspensory  ligament,  and  ciliary 
processes. 

The  ciliary  processes,  seventy  or  more  in  number, 
consist  of  a  circle  of  folds  or  thickenings  of  the  choroid 
received  into  pits  in  the  vitreous  and  suspensory 
ligament  of  the  lens.  They  are  divided  into  a  larger 
and  a  smaller  set,  the  former  being  about  one-tenth 
inch  in  length.  Their  inner  surface  is  covered  by  the 
layer  of  hexagonal,  pigmented  cells  in  the  retina. 

The  Retina. — ^This  is  a  delicate  nervous  membrane  on 
which  the  image  of  perceived  objects  is  formed.  It  lies 
between  the  choroid  and  the  hyaloid  membrane  of  the 
vitreous  humor,  and  is  composed  of  ten  layers  of  cells. 
Behind,  the  optic  nerve  expands  into  it,  and  in  front  it 

26 


402 


THE  ORGANS  OF  SPECIAL  SENSE 


terminates  in  a  dentated  margin,  the  ora  serrata,  at  the 
outer  edge  of  the  ciliary  processes.  It  then  sends  off 
a  thin,  non-nervous  membrane,  the  pars  ciliaris 
retinae,  to  the  tips  of  the  cihary  processes.  The  inner 
surface  of  the  retina  presents  at  its  centre  an  elHptical 


Fig.  141 


Canal  of  Schlemm. 


Posterior 
chamber. 

Ciliary 

body. 


Ciliary 
processes. 


Canal 
Feti 


\i 

Canal  for 
„„ — central  artery. 

1, 

w.. 

,   >r^^- 

— 'Optic  nej'VB. 

Sclerotic  coat. 

Nerve  sheath. 
A  horizontal  section  of  the  eye-ball.     (Allen.) 

spot  about  2ir  inch  across,  the  macula  lutea.  In  the 
centre  of  this  spot  is  a  depression,  the  fovea  centralis, 
which,  on  account  of  the  extreme  thinness  of  the  retina, 
shows  the  pigmentary  layer  of  the  choroid,  and  hence 


THE  SENSE  OF  SIGHT  403 

presents  the  appearance  of  a  foramen.  About  yV 
inch  to  the  inner  side  of  the  yellow  spot  is  the  porus 
opticus,  at  which  point  the  optic  nerve  enters,  the 
nervous  matter  being  heaped  up  here  so  as  to  forrn 
the  colliculus. 

Observed  under  the  microscope  the  retina  consists 
of  cell  elements  arranged  in  layers  as  follows: 

1.  The  layer  of  pigment  cells. 

2.  The  layer  of  rods  and  cones,  or  Jacobsen's  layer. 

3.  The  external  limiting  membrane. 

4.  The  outer  nuclear  or  granular  layer. 

5.  The  outer  molecular  or  reticular  layer. 

6.  The  inner  nuclear  or  granular  layer. 

7.  The  inner  molecular  or  reticular  layer. 

8.  The  layer  of  ganglion  cells. 

9.  The  layer  of  nerve  fibers. 

The  layers  in  the  retina  are  held  together,  except 
the  layer  of  rods,  and  cones,  by  a  fine  net-work  of 
neuroglia,  called  the  fibers  of  Muller. 

The  Function  of  the  Retina. — The  rods  and  cones 
are  the  most  important  layer  of  cell  elements  in  the 
retina  as  necessary  to  vision.  This  layer  possesses 
the  property  of  receiving  light  and  color  stimuli  which 
are  transformed  into  energy  that  arouses  nerve 
impulses  in  the  fibers  of  the  optic  nerve  and  the  latter 
convey  them  to  the  centre  of  vision  in  the  cerebrum 
(cuneus)  and  we  are  conscious  of  external  objects 
with  their  combined  colors,  etc.,  through  the  sense 
of  sight.  A  ray  of  light  passes  through  the  pupil, 
crystalline  lens,  and  vitreous  humor,  to  be  thrown  upon 
the  retina,  when  it  passes  through  all  the  layers  of 
the  retina  and  is  stopped  only  upon  reaching  the 
pigmentary  epithelium  in  which  the  rods  and  cones 
are  embedded.  Just  how  light  and  color  stimuli 
create  nerve  impulses  is  not  exactly  understood.  It 
is  supposed  to  be  due  to  ether  vibrations  being  trans- 
formed into  heat,  which  excites  the  rods  and  cones. 


404  THE  ORGANS  OF  SPECIAL  SENSE 

and  nerve  impulses  are  developed  which  are  conveyed 
to  the  brain. 

When  one  becomes  conscious  of  seeing  an  object, 
it  is  due  to  the  fact  that  an  image  has  been  formed 
by  the  rays  of  light  passing  through  the  pupil  and 
coming  in  contact  with  complex  structures  which 
are  termed  the  refracting  apparatus,  which  consists 
of  the  cornea,  aqueous  humor,  crystalline  lens,  and 
vitreous  humor.  The  rays  of  light  must  pass  through 
these  structures,  and  as  they  pass  from  one  to  the 
other  they  are  changed  in  direction  by  their  surfaces 
and  are  narrowed  to  a  single  point  of  focus  on  the 
retina.  Thus  if  the  rays  of  light  coming  from  various 
directions  and  distances  were  not  focussed,  the  same  as 
an  object  on  the  lens  of  a  camera,  they  would  simply 
be  thrown  on  the  retina  and  create  the  sensation  of 
diffused  light  rays,  and  form  an  indistinct  image  on 
the  retina. 

Accommodation. — This  is  the  term  expressing  the 
power  possessed  by  the  eye  of  adjusting  itself  to 
vision  at  different  distances;  or  the  power  of  focussing 
rays  of  light  on  the  retina,  which  come  from  different 
distances  at  different  times  (Brubaker's  Physiology), 
In  other  words,  the  eye  cannot  see  two  different  objects 
at  different  distances,  and  both  be'  distinctly  seen. 
If  the  eye  looks  at  the  distant  object  the  near  object 
is  not  clear,  and  then  when  the  eye  focusses  on  the  near 
object  the  distant  one  is  indistinct. 

Accommodation  is  regulated  mainly  by  the  changes 
in  the  shape  of  the  lens  produced  by  the  action  of  the 
ciliary  muscle;  and  the  pupil  becoming  decreased  or 
increased  in  circumference. 

The  change  in  the  shape  of  the  lens  is  the  means 
by  which  the  eye  accommodates  itself  to  vision. 
How  this  mechanism  of  accommodation  is  produced 
is  not  definitely  settled.  However,  it  is  supposed  to 
be  due  to  the  anatomic  relation  between  the  ciliary 


THE  SENSE  OF  SIGHT  405 

muscle  and  suspensory  ligament.  The  former  is 
attached  to  the  ligament,  and  the  ligament  is  the 
supporting  structure  of  the  lens.  If  the  eye  is'  looking 
at  a  near  object  the  lens  becomes  more  convex  or 
bulges  in  front.  This  is  produced  by  the  ciliary 
muscle  contracting  and  relaxing  the  ligament  which 
permits  the  lens  to  bulge  forward  and  become  more 
convex — due  to  its  elasticity.  The  nearer  an  object 
is  to  the  eye  the  greater  will  be  the  divergence  of  the 
rays  of  light,  and  as  a  result  the  lens  becomes  more 
convex  in  order  to  converge  and  focus  the  rays  upon 
the  retina,  so  that  the  image  will  be  distinct.  If 
the  eye  is  looking  at  a  distant  object  the  lens  is  less 
convex.  The  further  away  an  object  is  from  the  eye, 
the  less  divergent  will  be  the  rays  of  light.  Thus  the 
lens  is  not  called  upon  to  converge  the  rays  of  light  as 
they  fall  upon  the  retina  to  appear  distinct,  as  is  the 
case  in  looking  at  a  near  object.  At  the  same  time  the 
pupil  also  becomes  narrowed  to  prevent  an  indistinct- 
ness of  the  image  by  permitting  an  excess  of  light 
rays  to  pass.  These  would  otherwise  be  too  diffuse, 
due  to  the  angle  at  which  they  enter,  to  permit  of  a 
proper  focussing  of  the  image  on  the  retina. 

In  seeing  an  object  both  eyes  are  involved,  and  two 
images,  one  in  each  eye,  are  focussed  upon  the  retina, 
but  there  arises  only  one  sensation.  This  is  due  to  the 
fact  that  both  eyes  converge  toward  the  object  seen, 
and  it  is  focussed  as  an  image  upon  the  fovese  at 
corresponding  points,  in  each  retina.  When  any 
condition  interferes  with  the  proper  convergence  of 
the  eyes  toward  an  object,  double  vision  occurs,  due 
to  the  object  falling  on  two  different  points  of  the 
retina. 

The  function  of  the  iris  is  to  regulate  the  quan- 
tity of  light  entering  the  interior  of  the  eye  and  adjust 
the  rays  of  light  so  that  the  formation  and  perception 
of  an  image  shall  be  distinct. 


406     THE  ORGANS  OF  SPECIAL  SENSE 

This  diaphragm-like  action  of  the  iris  is  produced 
by  the  contraction  and  relaxation  of  the  muscle  fibers 
contained  therein — sphincter  pupillae  and  dilator  pupillse 
muscles.  The  contraction  of  the  sphincter  pupilhe  is 
reflex  and  is  spoken  of  as  the  iris  reflex. 


THE    ANATOMY    AND    PHYSIOLOGY    OF    THE 

STRUCTURES    CONCERNED   IN    THE 

SENSE  OF  TASTE 

The  structures  concerned  in  the  sense  of  taste 
include  the  tongue  and  its  taste-buds,  and  the  nerves 
conveying  the  sensations  to  the  taste  centre  situated 
in  the  fourth  temporal  convolution  of  the  temporal 
lobe  of  the  cerebrum,  where  the  nerve  impulses  give 
rise  to  the  sensations  of  taste.  The  stimuli  to  create 
these  nerve  impulses  is  matter,  organic  and  inorganic, 
in  a  state  of  solution,  as  brought  about  by  the  actions 
of  mastication  and  insalivation. 

The  End-organs  or  Taste-buds.— They  are  ovoid 
bodies  embedded  in  the  epithelial  cells  covering  the 
mucous  membrane  of  the  tongue,  soft  palate,  and 
posterior  surface  of  the  epiglottis.  Their  broadest 
portion  or  base  rests  on  the  basement  membrane  and 
the  apex  reaches  the  surface  of  the  epithelial  cells, 
when  it  opens  by  means  of  a  narrow  funnel-shaped 
opening  called  the  taste-pore.  The  wall  of  the  taste- 
buds  consists  of  long,  slender,  epithelial  cells,  within 
which  are  narrow  spindle-shaped  neuro-epithelial  cells, 
which  give  off  hair-like  processes  which  project  into 
the  taste-pore;  these  neuro-epithelial  cells  connect 
with  the  filaments  of  the  glossopharyngeal  and  chorda 
tympani  nerves  (gustatory  nerves),  and  are  considered 
as  the  peripheral  end-organs  of  the  nerves  of  taste, 
called  taste-buds  or  taste-beakers. 

Sensations  of  Taste. — It  must  be  remembered  the 


THE  SENSE  OF  HEARING  407 

tongue  also  possesses  the  property  of  conveying 
impulses  which  give  rise  to  sensations  of  touch  and 
temperature,  and  these  make  the  classification  of 
sensations  of  taste  most  difficult.  However,  the  tastes 
have  been  classified  into  four  primary  groups:  bitter, 
sweet,  acid,  or  salt.  The  intensity  of  the  sensation  of 
taste  produced  by  any  one  of  these  groups,  or  a  com- 
bination of  them,  is  dependent  upon  their  concentra- 
tion; and  the  extent  of  the  sensation  depends  on  the 
area  affected,  or  the  number  of  taste-buds  coming  in 
contact  with   them. 


THE    ANATOMY    AND   PHYSIOLOGY   OF   THE 

STRUCTURES     CONCERNED     IN     THE 

SENSE    OF   HEARING 

The  Ear. — The  ear  is  divided  into  the  external  ear, 
the  middle  ear  or  tympanum,  and  the  internal  ear  or 
labyrinth. 

The  External  Ear. — This  consists  of  the  projecting 
part,  or  pin7ia,  and  the  external  auditory  canal  and 
meatus.  The  pinna,  or  auricle,  is  ovoid  in  outline, 
concave  externally,  and  facing  outward  and  somewhat 
forward,  presenting  eminences  and  depressions,  to 
which  various  names  have  been  given. 

The  pinna  consists  of  a  plate  of  yellow  fibrocartilage 
covered  by  skin  and  some  adipose  tissue.  It  enters 
also  into  the  formation  of  the  external  meatus,  being 
attached  to  the  margins  of  the  external  auditory  meatus 
of  the  temporal  bone.  The  lobule  contains  only  fat 
and  strong  fibrous  tissue. 

The  external  auditory  canal  is  IJ  inches  long  (adult), 
and  runs  from  the  concha  to  the  membrana  tympani. 
It  is  directed  obliquely  forward,  inward,  and  downward, 
and  presents  an  eminence  in  the  floor  of  the  osseous 
part,  which  makes  the  direction  of  the  canal  at  first 


408  THE  ORGANS  OF  SPECIAL  SENSE 


upward  and  then  downward.  It  is  narrowest  at  its 
middle.  It  opens  externally  by  means  of  the  external 
auditory  meatus. 

The  Middle  Ear  or  Tympanum. — This  is  a  cavity  in 
the  petrous  portion  of  the  temporal  bone,  extending 
from  the  membrana  tympani  to  the  outer  wall  of  the 
labyrinth.  Its  width  varies  from  yV  to  \  inch.  It 
contains  the  ossicles  of  the  ear,  with  their  ligaments 
and  muscles,  and  certain  nerves.  It  is  filled  with  air 
and  communicates  by  means  of  the  Eustachian  tube 
with  the  nasopharynx. 


Fig.  142 


Cartilage  of 
the  pinna ' 


Promont. 


Cartilage  of  the  ext. 
auditory  meatuiy 


Transverse  section  of  external  auditory  meatus  and  tympanum.    (Gegenbaur  ) 


The  membrana  tyvijMni  is  a  thin  membrane  inserted 
into  a  ring  of  bone  at  the  bottom  of  the  external 
canal,  which  is  grooved  for  its  reception.  It  is  ovoid 
in  form  and  directed  obliquely  downward  and  inward. 
On  its  inner  surface  is  the  handle  of  the  malleus,  which 
extends  from  about  the  middle  of  its  roof  to  a  little 
below  its  centre,  covered  by  mucous  membrane,  where 


THE  SENSE  OF  HEARING 


409 


it  is  attached.  This  process  draws  the  membrane 
inward,  making  its  outer  surface  concave  and  its 
inner  convex.  Externally,  the  membrane  is  covered 
with  skin,  continuous  with  that  of  the  meatus;  inter- 
nally, with  mucous  membrane  continuous  with  that 
of  the  tympanum;  and  between  these  two  is  a  fibrous 
layer,  some  of  its  fibers  radiating  from  the  handle 
of  the  malleus,  others  being  circular  and  placed  near 
the  circumference. 

Fig.  143 


Chorda  tympani. 


View  of  inner  wall  of  tympanum.     (Gray.) 


The  i7mer  wall  of  the  tympanum  is  vertical  and 
uneven.  It  presents  the  following:  (a)  The  fenestra 
ovalis,  leading  into  the  vestibule,  and  occupied  in  the 
recent  state  by  the  base  of  the  stapes  and  its  annular 
ligament.  (6)  Fenestra  rotunda,  in  a  conical  fossa 
leading  into  the  cochlea,  a  rounded  eminence,  (c)  The 
2?romontory,  separating  it  from  the  preceding.  It  is 
closed,  in  the  recent  state,  by  the  memhrana  tympani 
secundaria.  This  is  composed  of  three  layers,  and  is 
concave  toward  the  tympanum. 


410     THE  ORGANS  OF  SPECIAL  SENSE 

The  posterior  wall  of  the  tympanum  presents  above 
one  large  and  several  small  apertures  leading  to  the 
mastoid  cells. 

The  anterior  extremity  opens  into  two  canals  separ- 
ated by  a  process  of  bone,  the  processus  cochlcariformis. 
The  upper  of  these  canals  is  the  smaller  and  transmits 
the  tensor  tympani;  the  lower  contains  the  Eustachian 
tube,  an  osseocartilaginous  passage  l^^  inches  long, 
leading  to  the  pharynx.  Both  of  these  canals  run  in 
a  direction  downward,  forward,  and  inward. 

The  osseous  part  of  the  Eustachian  tube  is  ^  inch 
long,  and  to  its  lower  end  is  attached  the  triangular 
piece  of  fibrocartilage  forming  the  remainder  of  the 
tube.  The  edges  of  the  cartilage  are  now  in  contact, 
but  are  joined  by  fibrous  tissue.  The  tube  is  wide 
at  its  lower  extremity,  and  opens  at  the  upper  and 
lateral  part  of  the  pharynx,  above  the  hard  palate  and 
on  a  line  with  the  lower  turbinated  bone.  It  is  lined 
by  epithelium  continuous  with  that  of  the  pharynx. 

The  ossicles  are  three  minute  movable  bones,  named 
the  malleus,  incus,  and  stapes.  The  first  is  attached 
to  the  membrana  tympani;  the  second  is  between  the 
other  two;  the  last  named  is  attached  to  the  fenestra 
ovalis  of  the  cochlea. 

The  Muscles  of  the  Middle  Ear. — The  tensor 
tympani  runs  in  the  canal  previously  mentioned. 
Arising  from  the  under  surface  of  the  petrous  portion, 
the  cartilage  of  the  Eustachian  tube,  and  the  margins 
of  its  own  canal,  its  tendon  is  reflected  over  •  the 
processus  cochlcariformis  and  is  inserted  into  the 
handle  of  the  malleus  near  its  root.  It  pulls  on  the 
malleus,  thus  drawing  inward  and  making  tense  the 
membrana  tympani.  Its  nerve  comes  from  the  optic 
ganglion. 

The  stapedius  muscle  arises  from  the  sides  of  its  con- 
taining cavity  within  the  pyramid,  and,  emerging  from 
the  apex,  is  inserted  into  the  neck  of  the  stapes.    It 


THE  SENSE  OF  HEARING  411 

draws  the  head  of  the  stapes  backward,  thus  pressing 
the  base  against  the  fenestra  ovaUs  and  compressing 
the  contents  of  the  vestibule.  Its  nerve  is  the  tympanic 
branch  of  the  facial. 

The  Internal  Ear. — This  is  the  essential  part  of  the 
hearing  apparatus,  since  here  the  auditory  nerve  is 
distributed.  It  is  contained  in  a  cavity  in  the  petrous 
bone,  and  is  made  up  of  the  osseous  labyrinth  and 
the  membranous  labyrinth. 

The  osseous  labyrinth  contains  the  membranous 
labyrinth,  and  is  divided  into  three  parts,  the  vesti- 
bule, semicircular  canals,  and  cochlea.  It  communi- 
cates in  the  dry  state  with  the  tympanum  by  means 
of  the  fenestrse.  Between  the  osseous  and  mem- 
branous labyrinth  is  a  space  occupied  by  a  clear  fluid, 
the  perilymph,  and  within  the  membranous  labyrinth 
is  the  endolymph. 

The  vestibule  is  the  central  cavity  lying  between 
the  cochlea  in  front  and  the  semicircular  canal  behind, 
the  tympanum  being  external.  Its  outer  or  tympanic 
wall  presents  the  fenestra  ovalis. 

Its  inner  wall  has  in  front  a  depression,  the  fovea 
hemispherica,  pierced  by  several  minute  holes  for 
the  auditory  filaments,  and  behind  this  a  ridge,  the 
crista  vestibuli.  Behind  this  ridge  is  the  opening  of 
the  aqiieductus  vestibuli.  In  the  roof  is  a  depression, 
the  fovea  heinielUytica. 

Behifid,  the  vestibule  presents  five  foramina  leading 
into  the  semicircular  canals,  and  in  front  a  larger 
foramen  leading  into  the  scala  vestibuli  of  the  cochlea. 

The  semicircular  canals  are  three  bony  tubes  of 
unequal  length  lying  above  and  behind  the  vestibule, 
each  forming  about  two-thirds  of  a  circle.  Their 
general  diameter  is  tjV  inch,  but  at  one  end  is  a  dila- 
tation, the  ampulla,  y  q  inch  in  diameter.  They  empty 
into  the  vestibule  by  five  apertures,  in  one  of  which 
two  tubes  join. 


412 


THE  ORGANS  OF  SPECIAL  SENSE 


The  cochlea  resembles  a  snail  shell.  Its  apex  looks 
forward  and  outward,  and  its  base  toward  the  internal 
auditory  meatus.  Within  is  a  centre  piece,  the  modiolus 
or  colmnella,  around  which  the  canal  runs  spirall}^  for 
two  and  one-half  turns. 

Within  the  canal,  and  attached  to  the  modiolus,  is 
the  lamina  spiralis.  This  plate  of  bone  partially 
divides  the  spiral  canal  into  two  compartments  or 
scalse,  the  division  being  completed  by  a  membrane 


Fia.  144 


PHATIC    CANAL 


CANALIS 
REUNIENS 


Membranous  labyrinth  of   the  right  ear,  viewed  from  the   outer  side; 
semidiagrammatic.    (Testut.) 

which  reaches  the  outer  w^all  of  the  cochlea.  The 
upper  scala  is  known  as  the  scala  vestibuli;  the  lower 
is  the  scala  tyinjmni. 

The  membranous  labyrinth  is  contained  within  the 
osseous  labyrinth,  having  a  similar  form,  though 
smaller  and  separated  from  it  by  the  perilymph.  It 
contains  the  endolymph  and  receives  the  distribution 
of  the  auditory  nerve.  In  the  vestibule  it  consists  of 
the  utricle  and  the  saccule. 

The  memhraiious  semicircular  canals  are  similar  in 
shape  to,  but  are  only  from  one-fifth  to  one-third  the 


THE  SENSE  OF  HEARING 


413 


diameter  of,  the  bony  canals;  the  ampullae,  however, 
are  relatively  large.  Two  small  masses  of  calcium 
carbonate  are  found  in  the  utricle  and  saccule.  They 
are  called  the  otoliths. 

In  the  cochlea  the  membranous  labyrinth  is  repre- 
sented by  the  scala  media  and  the  parts  therein 

The  Organ  of  Corti. — It  extends  the  entire  length 
of  the  cochlea.    It  consists  of  two  modified  epithelial 

Fig.   145 


Organ  of  Corti.    Diagrammatic  view  of  a  small  portion.    (Testut.) 


cells  resting  upon  a  basement  membrane  and  joined 
above  to  form  an  arch  which  encloses  a  tunnel  or 
canal  of  Corti;  it  also  consists  of  a  series  of  columnar 
epithelial  cells  with  hair-like  processes  (hair  cells) 
which  rest  upon  and  are  supported  by  the  rods  both 
on  the  inner  and  .outer  side.  Other  cells  lie  adjacent 
to  the  hair  cells,  and  are  supportive  in  character; 
these   are   called    Deiters'    cells. 

The   rods   of   Corti   are   very   numerous,    reaching 
up    into    the    thousands.      The    hair-like    processes 


414  THE  ORGANS  OF  SPECIAL  SENSE 

covering  the  rods  of  Corti  are  bathed  by  a  clear  fluid, 
the  endolymph.  This  fluid  comes  from  the  sub- 
arachnoid lymph  spaces  at  the  base  of  the  brain. 

The  hair  cells  resting  on  the  organ  of  Corti  are 
practically  end-organs  of  the  cochlear  branch  of  the 
auditory  nerve.  Just  how  the  filaments  of  this  nerve 
come  in  direct  contact  with  these  cells  and  develop 
nerve  impulses  is  not  definitely  understood. 

The  Physiology  of  the  Structures  Concerned  in 
the  Sense  of  Hearing. — The  sense  of  hearing  is  based 
on  the  functions  possessed  by  the  structures  within  the 
three  portions  of  the  ear,  which  receive  and  transmit 
atmospheric  vibrations  set  up  in  the  external  world 
about  us,  to  the  sensitive  hair  cells  of  the  organ  of 
Corti,  where  they  are  taken  up  and  carried  back  by 
the  fibers  of  the  auditory  nerve  to  the  centres  in  the 
cerebrum  and  the  brain  becomes  conscious  of  the 
sensations  of  sound. 

Stimuli. — ^All  stimuli  which  produce  the  sense  of 
sound  must  be  in  a  state  of  motion,  and  thus  create 
vibrations  which  are  communicated  to  the  air  in 
which  they  are  moving  to  and  for,  setting  it  into 
waves,  called  sound  waves.  These  sound  waves  in 
turn  reach  the  tympanic  membrane  through  the 
external  auditory  canal,  and  set  it  into  vibration; 
then  they  are  transmitted  to  the  structures  of  the 
internal  ear  by  means  of  the  ossicles  and  structures 
within  the  middle  ear  which  convey  vibrations  to  the 
endolymph  in  the  internal  ear  and  the  latter  stimulate 
the  hair  cells  in  relation  with  the  organ  of  Corti.  From 
the  latter  end-organ  they  are  transmitted  to  the 
centres  of  hearing  in  the  brain  through  the  fibers  of 
the  auditory  nerve. 

Vibrations  producing  sound  waves  in  the  atmosphere 
are  communicated  to  it  by  means  of  the  moving  to 
and  fro  of  elastic  bodies  as  tuning  forks,  rods,  strings, 
membranes,  etc. 


QUESTIONS  415 

Sound. — Sounds  which  arise  as  the  result  of  impact 
and  transmission  of  the  effects  of  sound  waves  are 
said  to  possess  intensity,  pitch,  and  quaUty  or  tone. 

Intensity. — When  we  speak  of  the  intensity  of  a 
sound  it  means  the  loudness. 

Pitch. — Pitch  of  a  sound  depends  upon  the  number 
of  vibrations  which  strike  the  ear  in  a  unit  of  time,  a 
second.  The  greater  the  number  of  vibrations  the 
higher  the  pitch  and  vice  ver§a. 

Quality. — Quality  of  a  sound  depends  upon  the 
form  of  the  vibration.  The  form  of  the  sound  wave 
in  any  given  instance  is  the  resultant  of  a  combination 
of  a  fundamental  vibration  and  certain  secondary 
vibrations  of  subdivisions  of  the  vibrating  body. 
These  secondary  vibrations  give  rise  to  what  is  known 
as  overtones.  B}'  their  union  with  and  modification  of 
the  fundamental  vibration  there  is  produced  a  special 
form  of  vibration  which  gives  rise  not  to  a  simple  but 
to  a  composite  sensation.  It  is  for  this  reason  that  the 
same  note  of  the  piano,  the  violin,  and  the  human 
voice  varies  in  quality  (Brubaker). 


QUESTIONS 

1.  Name  some  of  the  ordinary  sensations. 

2.  Name  some  of  the  special  sensations.    How  do  they  arise? 

3.  Name  the  special  senses. 

4.  What   structures   are   essential   for   the    appreciation   of   the 
sense  of  touch? 

5.  Name   some   of   the   end-organs   concerned   in   the    sense    of 
touch. 

6.  Where  are  the  corpuscles  of  Meissner  located?     Of  Vater? 

7.  What  do  you  understand  by  the  sense  of  touch? 

8.  Name  the  senses  possessed  by  the  skin. 

9.  What  does  the  individual  perceive  by  the  muscle  sense? 

10.  What  structures  are  essential  to  the  sense  of  smell? 

11.  Bound  the  nasal  fossae. 

12.  Name  the  two  portions  into  which  the  mucous  membrane  of 
the  nasal  fossse  is  divided. 

13.  What  type  of  epithelium  is  found  in  the  olfactory  portion 
of  the  nasal  mucous  membrane? 

14.  Name  the  appendages  of  the  eye. 


416     THE  ORGANS  OF  SPECIAL  SENSE 

15.  What  structures  are  included  under  the  lacrymal  apparatus? 

16.  How  many  lacrymal  ducts  are  there  and  where  do  they  drain? 

17.  How  do  the  tears  reach  the  nasal  cavity? 

18.  Name  the  coats  of  the  eye-ball. 

19.  What  muscle  controls  the  diameter  of  the  pupil? 

20.  What  structure  contains  the  pigment  which  gives  the  eye 
its  color? 

21.  Where  is  the  vitreous  humor  found  in  the  eye?  The  aqueous? 
The  crystalline  lens? 

22.  Where  is  the  anterior  chamber  of  the  eye?  The  posterior 
chamber? 

23.  What  is  the  function  of  the  retina? 

24.  What  nerve  expands  into  the  retina  and  when  does  the 
nerve  enter  it? 

25.  How  many  layers  of  cells  in  the  retina?  Which  layer  of  cells 
is  the  most  important  as  regards  vision? 

26.  Name  the  refracting  apparatus  of  the  eye. 

27.  What  is  accommodation  as  regards  vision?  What  is  the 
function  of  the  lens  in  relation  to  accommodation? 

28.  What  is  the  function  of  the  iris? 

29.  Name  the  structures  concerned  in  the  sense  of  taste. 

30.  Where  are  the  end-organs  or  taste-buds  located? 

31.  Name  the  three  divisions  of  the  ear. 

32.  How  long  is  the  external  auditory  canal?  What  is  its  direc- 
tion? 

33.  Describe  the  tympanum  or  middle  ear. 

34.  Where  is  the  tympanic  membrane  located?  What  structure 
covers  its  outer  and  inner  surfaces? 

35.  Through  what  tube  does  the  tympanic  cavity  of  the  ear 
communicate  with  the  nasopharynx? 

36.  What  structures  are  included  under  the  term  internal  ear? 

37.  What  are  the  divisions  of  the  osseous  labyrinth  as  regard  its 
formation? 

38.  Where  is  the  membranous  labyrinth  located.  What  fluid 
does  it  contain. 

39.  What  fluid  separates  the  membranous  from  the  osseous 
labyrinth? 

40.  Where  is  the  organ  of  Corti  located? 

41.  What  relation  do  the  hair  cells  in  the  organ  of  Corti  bear  to 
the  auditory  nerve? 

42.  How  many  ossicles  are  there  in  each  middle  ear?  Name 
them. 

43.  In  what  state  must  all  external  stimuli  be  in  to  produce  the 
sense  of  sound. 

44.  How  do  vibrating  bodies  affect  the  atmospheric  air  as  regards 
the  sense  of  sound? 

45.  Give  a  brief  description  of  how  the  sound  waves  are  con- 
veyed from  the  external  air  to  the  filaments  of  the  auditory  nerve 
in  the  organ  of  Corti. 


CHAPTER  XIX 
ORGANS  OF  REPRODUCTION 


THE   EXTERNAL    ORGANS    OF   REPRODUCTION 

(FEMALE) 

The  Vulva. — The  term  vulva,  or  pudendum,  includes 
the  mons  veneris  and  labia,  the  nymphse  and  clitoris, 
the  hymen  or  its  remains,  the  meatus  urinarius,  and 
the  vaginal  orifice. 

The  mons  veneris  is  a  fatty  cushion  covering  the 
front  of  the  pubes,  and  after  puberty  is  plentifully 
supplied  with  hairs.  Below,  it  divides  into  the  two 
labia  majora,  which  diminishing  in  size  as  they  pass 
downward  and  backward,  unite  an  inch  in  front  of 
the  anus.  The  two  extremities  are  joined,  and  form 
the  anterior  and  posterior  commissures.  Between  the 
latter  and  the  anus  is  the  perineum,  and  just  within 
the  posterior  commissure  is  a  transverse  fold,  the 
fourchette. 

The  nymphse,  or  labia  minora,  smaller  than  the 
above,  run  from  the  middle  of  the  labia  majora  up- 
ward to  the  clitoris,  each  dividing  into  two  folds, 
the  upper  pair  of  which  join  to  form  a  prepuce  for 
that  organ,  and  the  lower  two  to  form  its  frenum. 
They  are  continuous  externally  with  labia  majora, 
internally  with  the  vagina. 

The  clitoris  is  the  opposite  of  the  penis  (male),  con- 
sisting, like  it,  of  two  corpora  cavernosa  united  by  a 
septum  pectiniforme  and  prolonged  behind  into  two 
27 


418 


ORGANS  OF  REPRODUCTION 


crura  attached  to  the  rami  of  the  pubis  and  ischium 
(bones).     It  also  has  a  suspensory   Hgament   and   a 


Fig.  146 
mons  veneris 


.^ 


CLITORIS 


MEATUS 
-URINARIUS 


Vulva  of  a  virgin.  The  labia  have  been  widely  separated.  Foss.  nav., 
fossa  navicularis;  Int.  vag.,  introitus  vaginae;  Lab.  min,  labium  minus; 
Vestib.,  vestibule.     (Testut.) 


glans  enclosed  by  the  nymphse.  Two  erectores  cli- 
toridis  muscles  are  attached  to  the  crura.  It  has  no 
corpus  spongiosum  nor  urethra. 


THE  EXTERNAL  ORGANS  OF  REPRODUCTION    419 

Between  the  clitoris  and  the  vagina,  bounded  on 
each  side  by  the  nymphse,  is  the  vestibule,  a  triangular 
space,  in  which,  just  above  the  vagina,  is  the  opening 
of  the  urethra,  one  inch  below  the  clitoris. 

The  hymen  is  a  mucous  fold  which  more  or  less 
completely  occludes  the  opening  of  the  vagina.  It 
is  generally  semilunar  in  form,  concave  above,  or 
it  may  be  a  complete  membrane,  perforate  or  imper- 
forate, or  it  may  be  absent.  It  is  usually,  present  in 
a  virgin,  though  its  absence  does  not  prove  that  coitus 
has  been  performed. 

The  glands  of  Bartholin,  the  analogues  of  Cowper's 
glands  in  the  male,  are  two  yellowish  bodies  on  each 
side  of  the  vaginal  opening,  each  of  which  dis- 
charges by  a  single  duct  between  the  hymen  and  the 
nymphse. 

The  Urethra. — The  female  urethra  is  a  mucous 
canal,  1^  inches  long,  running  downward  and  forward 
in  the  anterior  vaginal  wall  from  the  neck  of  the 
bladder  to  the  meatus  urinarius  and  drains  the  urine 
from  the  bladder  during  micturition,  and  can  be  seen 
as  a  minute  opening  just  below  the  clitoris.  As  in 
the  male,  it  pierces  the  triangular  Hgament,  and  is 
surrounded  by  the  compressor  urethrse  muscle. 

The  Vagina. — The  vagina  extends  from  the  vulva 
to  the  uterus  (os  uteri),  lying  behind  the  bladder  and 
in  front  of  the  rectum,  and  is  about  4  inches  long  on 
its  anterior  wall,  5  to  6^  on  its  posterior,  and  is  directed 
from  the  uterus  downward  and  forward. 

Above,  it  embraces  the  cervix  uteri,  and  its  walls 
are  flattened  from  before  backward.  In  front  it  is 
in  relation  with  the  urethra  and  base  of  the  bladder; 
behind,  it  is  connected  with  the  anterior  wall  of  the 
rectum  by  its  lower  three-fourths,  the  cul-de-sac  of  peri- 
toneum (Douglas')  separating  them  in  the  upper  fourth; 
laterally,  the  broad  ligaments  are  attached  above,  and 
the  levatores  ani  below,  as  well  as  the  rectovesical  fascia. 


420  ORGANS  OF  REPRODUCTION 

Its  inner  surface  presents  a  mesial  ridge  or  raphe  on 
the  front  and  back  walls,  the  columnse  rugarum,  and 
from  them  on  both  sides  run  out  transverse  folds  or 
rugae. 


THE  INTERNAL  ORGANS  OF  REPRODUCTION 

(FEMALE) 

The  internal  organs  include  the  uterus,  tubes,  and 
ovaries. 

The  Uterus. — The  uterus  or  womb  is  a  hollow  mus- 
cular organ  lying  in  the  pelvis  between  the  bladder 
and  rectum.  In  the  virgin  it  is  pear-shaped,  flattened 
from  before  backward,  its  upper  end  looking  forward 
and  upward,  its  lower  downward  and  backward, 
forining  an  angle  with  the  vagina.  Above,  it  is  invested 
by  the  peritoneum,  which  covers  its  body  before  and 
behind;  it  covers  also  the  cervix  behind,  but  in 
front  the  peritoneum  is  reflected  on  to  the  bladder 
before  reaching  the  cervix.  The  two  folds  of  peri- 
toneum after  investing  the  uterus  are  applied  to  each 
other,  reaching  across  to  the  lateral  pelvic  walls  forming 
the  broad  ligaments. 

The  uterus  is  3  inches  long,  2  wide,  and  1  thick, 
and  it  weighs  about  1  ounce.  It  is  divided  into  a 
body,  fundus,  and  neck.  The  fundus  is  the  convex 
part  above  the  entrance  of  the  tubes;  the  body  is  the 
part  between  this  and  the  neck.  In  front  of  the 
Fallopian  tubes,  at  the  upper  part  of  the  lateral 
borders,  the  round  ligaments  are  attached,  and  below 
and  behind  them  are  the  ligaments  of  the  ovaries. 
The  cervix  is  the  lower  constricted,  rounded  part,  and 
around  it  is  attached  the  vagina.  At  its  vaginal  end 
is  a  round  opening,  the  os  uteri. 

The  cavity  of  the  uterus  is  small;  that  part  within 
the   body   is   triangular,   flattened   anteroposteriorly, 


THE  INTERNAL  ORGANS  OF  REPRODUCTION     421 

and  presents  at  the  superior  angles  the  openings  of 
the  Fallopian  tubes;  also,  at  its  junction  with  the 
neck  it  is  constricted  to  form  the  os  internum.  The 
cavity  of  the  cervix  is  barrel-shaped  and  flattened 
anteroposteriorly,  presenting  on  each  wall  a  longi- 
tudinal column  sending  off  oblique  rugae  on  each  side; 
hence  its  name,  arbor  vitae  uterinus. 


TUBAL  VESSELS 


FlQ.     147 


ANASTOMOSIS  OF  FALLOPIAN 

UTERINE    AND  TU.BE 

OVARIAN  ARTERIES 
HCLICINE    BRANCHES         \ 


ROUND    LIGAMENT 


VAGINAL  VENOUS    PLEXUS 


TERINE   ARTERY 


'^l     SUPERIOR   VAGINAL 
ARTERIES 


OS    UTERI        VAGINA    CUT   OPEN    BEHINO 

Vessels  of  the  uterus  and  its  appendages,  rear  view.     (Testut.) 


The  walls  of  the  uterus  consist  of  an  outer  serous 
coat,  an  inner  mucous,  and  an  intermediate  muscular. 
The  muscular  coat  forms  the  bulk  of  the  uterus, 
and  consists  of  bundles  and  layers  of  unstriped  fibers 
which  interlace,  and  of  some  areolar  tissue  sup- 
porting them,  and  of  bloodvessels,  lymphatics  and 
nerves. 

The  mucous  membrane  of  the  body  differs  from  that 
of  the  cervix.  The  former  is  smooth,  reddish,  with 
columnar  cells,  and  presents  the  ducts  of  a  number  of 
tubular  glands  which  end  by  blind,  sometimes  forked, 
extremities.     In  the  cervix  it  is  firmer,  and  presents 


422  ORGANS  OF  REPRODUCTION 

numerous  saccular  and  tubular  glands  between  the 
rugae  of  the  arbor  vitse,  and  below,  numerous  papillae. 

The  ligaments  of  the  uterus  are  the  round  ligaments 
and  several  yeritoneal  folds,  namely,  two  each  in  front, 
behind,  and  laterally. 

The  round  ligaments  are  two  cord-like  bundles  of 
areolar,  fibrous,  and  plain  muscular  tissue,  wdth 
vessels  and  nerves,  covered  by  peritoneum,  which 
run  from  the  upper  angle  of  the  uterus  to  the-  internal 
abdominal  ring.  Each  then  runs  through  the  corre- 
sponding inguinal  canal  to  end  in  the  mons  veneris 
and  labia. 

The  anterior  or  vesico-uterine  ligaments  stretch  bet- 
w^een  the  bladder  and  the  uterus;  the  posterior,  between 
the  uterus  and  rectum,  hence  called  the  recto-uterine, 
forming  a  pouch  of  peritoneum,  the  cul-de-sac  of 
Douglas. 

The  two  lateral  or  hroad  ligaments  pass  from  the 
sides  of  the  uterus  to  the  sides  of  the  pelvis,  thus 
dividing  the  latter  into  two  parts.  They  are  formed 
by  the  coalescence  of  the  peritoneal  layers  investing 
the  anterior  and  posterior  surfaces  of  the  uterus,  and 
contained  betw^een  the  two  layers — the  Fallopian 
tube  at  the  upper  margin ;  the  round  ligament  below 
and  in  front  of  the  tube;  the  ovary  and  its  ligament 
enfolded  by  the  posterior  layer;  and  the  uterine 
bloodvessels,  lymphatics,  and  nerves. 

Appendix. — The  Function  of  the  Uterus. — The  uterus 
receives  and  affords  a  surface  for  the  growth  and 
development  of  the  fecundated  ovum  and  its  mem- 
branes, which  become  the  embryo,  nourished  from  the 
placenta  (after  the  third  month),  and  retains  it  until 
the  foetus  is  fully  developed  (nine  months),  when,  by 
a  contraction  of  its  muscular  walls,  the  offspring  is 
delivered  through  the  vagina. 

The  Fallopian  Tubes. — The  Fallopian  tubes  or  ovi- 
ducts run  from  the  upper  angles  of  the  uterus 
toward  the  sides  of  the  pelvis,  and  near  their  termina- 


THE  INTERNAL  ORGANS  OF  REPRODUCTION     423 

tion  bend  downward,  backward,  and  inward.  They 
are  3  to  4  inches  long,  are  at  first  narrow,  then  enlarge 
near  the  extremity  (ampulla),  and  end  in  a  fimbriated 
margin,  one  of  the  fimbriae  being  attached  to  the 
ovary.  The  canal  is  very  narrow  at  the  uterine  end 
(ostium  uterinum),  begins  to  widen  in  the  outer  half 
to  form  the  ampulla,  and  at  its  termination  again 
narrows  (ostium  abdominale). 

The  tubes  consist  of  a  peritoneal  coat,  a  muscular 
coat  composed  of  internal  circular  and  external  longi- 
tudinal fibers,  and  a  mucous  coat.  The  latter  is  con- 
tinuous at  the  inner  aspect  of  the  tube  with  the  mem- 
brane of  the  uterus,  where  it  opens;  and  at  the  outer 
extremity  is  continuous  with  the  peritoneum  and 
communicates  with  the  peritoneal  cavity.  The 
epithelium  is  of  the  ciliated  columnar  variety,  and  is 
thrown  into  longitudinal  folds,  more  marked  in  the 
outer  half  of  the  tube. 

The  Ovaries.  —  The  ovaries  correspond  to  the 
testicles  in  the  male,  as  far  as  the  sex  relation 
is  concerned,  and  produce  the  ovum  or  germ  cell. 
They  are  flattened,  oval  bodies,  measuring  1^  inches 
long,  f  inch  wide,  and  ^  i^^^h  thick;  each  w^eigh 
60  to  100  grains.  They  are  located  in  the  ab- 
dominal cavity  on  either  side  of  the  uterus,  lodged 
in  the  folds  of  peritoneum  called  the  broad  ligaments 
of  the  uterus.  The  sides  of  each  one  and  the  convex 
border  are  free,  while  the  straight  border  is  attached 
to  the  broad  ligament  and  receives  the  bloodvessels, 
etc.,  at  this  point. 

Its  outer  end  is  attached  to  the  Fallopian  tube  by 
the  fimbria  ovarica,  its  inner  end  to  the  uterus  by 
the  ligament  of  the  ovary,  a  dense,  fibromuscular  cord 
attached  to  the  uterus  below  and  behind  to  the  tube. 

The  Structure  of  the  Ovary. — It  consists  of  an  external 
thin  connective-tissue  membrane,  and  an  internal  thin 
connective-tissue  stroma,  which  supports  the  blood- 
vessels, nerves,   and  non-striated  muscle  fibers,   and 


424 


ORGANS  OF  REPRODUCTION 


contain  in  its  meshes  the  Graafian  follicles.  These 
consist  of  spheric  sacs  and  are  present  in  large  numbers 
from  the  time  of  birth  to  the  period  of  the  menopause 
(change  of  life).  Each  follicle  consists  of  an  external 
investment  of  fibrous  tissue  and  bloodvessels,  and 
an  internal  investment  of  cells,  the  membrana  granu- 
losa. At  the  lower  portion  of  this  membrane  there  is 
an  accumulation  of  cells,  called  the  proligerous  disk. 
The  cavity  of  each  Graafian  follicle  contains  fluid. 

Fig.  148 


Section  of  the  ovary:  1.  Outer  covering,  l'.  Attached  border.  2.  Central 
stroma.  3.  Peripheral  stroma.  4.  Bloodvessels.  5.  Graafian  follicles  in 
their  earliest  stage.  6,  7,  8.  More  advanced  follicles.  9.  An  almost  mature 
follicle.  9'.  Follicle  from  which  the  ovum  has  escaped.  10.  Corpus  luteum. 
(After  Schron.) 


yellowish  in  color,  alkaline,  and  is  composed  of  albu- 
minous material.  -From  the  Graafian  follicle,  and  par- 
ticularly the  proligerous  disk,  the  ovum  or  germ  cell 
is  developed. 

The  Ovum  or  Germ  Cell. — This  is  a  spheric  body 
measuring  0.3  mm.  in  diameter.  It  consists  of  a 
mass  of  living  protoplasmic  material,  cytoplasm; 
a  nucleus  or  germinal  vesicle,  within  which  is  seen  a 
nucleolus  or  germinal  spot. 


THE  INTERNAL  ORGANS  OF  REPRODUCTION     425 

The  cytoplasm  surrounding  the  germinal  vesicle 
is  granular  in  appearance,  and  is  called  the  vitellus; 
the  outer  margin  of  the  cytoplasm  is  surrounded  by 
a  delicately  striated  border  called  the  zona  pellucida. 

The  ovum  is  the  cell  which  is  fertilized  by  the 
spermatozoon  of  the  male  and  develops  into  the  embryo 
and  its  ultimate  creation,  the  human  being — the 
infant. 


Fig.  149 


Theca^ 

folliculi' 

{fibrous  coat)j 


emhrana ' 

rantilosa 


Antrnn) 
foUici'H 
■th  liquin 
follic"'' 

rolifici  f  - 
scus  pro- 
ligerous) 
mm  vith^ 
na  j)('Uu- 
a,  germi- 
il  vesicle, 
id  germi- 

\l  spot  Ji/OOll- 


m 


V.y  •■:%■:■ 


vessel' 


Section  through  a  Graafian  follicle  from  an  ape's  ovary.     X  90. 
(Szymonowicz.) 

Ovulation. — This  is  the  term  used  to  describe  the 
process  whereby  the  mature  Graafian  follicle  ruptures 
and  the  ovum  is  forced  through  the  layers  of  the  ovary. 
When  the  female  reaches  the  age  of  puberty  (which  varies 
in  different  races  and  in  certain  climates)  the  Graafian 


426  ORGANS  OF  REPRODUCTION 

follicle  develops  and  ripens  or  matures  periodically, 
about  every  twenty-eight  days.  When  mature  the 
vesicle  ruptures  and  the  ovum  and  liquid  contents 
of  the  vesicle  are  discharged.  The  ovum  is  received 
by  the  fimbriated  extremity  of  the  Fallopian  tube, 
enters  its  cavity,  wherein  it  is  transferred  through  the 
tube  by  the  peristaltic  action  of  its  muscle  fibers,  aided 
by  the  cilia  of  the  lining  epithelial  cells,  into  the 
body  of  the  uterus,  where  it  is  fertilized,  when  mature, 
by  the  spermatozoa — the  germ  cell  of  the  male.  The 
ovum  may  be  fertilized  in  the  Fallopian  tube.  The 
passage  of  the  ovum  from  the  ovary  to  the  uterus 
occupies  approximately  four  to  ten  days.  The  ovum 
undergoes  a  succession  of  changes,  particularly  the 
nucleus,  after  it  leaves  the  ovary  before  fertilization 
can  occur.     (See  Maturation,  p.  35.) 

Corpus  luteum  is  a  yellowish  body  which  is  present 
in  the  ovum  following  the  rupture  of  the  Graafian 
follicle  and  the  ovum  escapes  into  the  oviduct  (ovula- 
tion). When  the  follicle  ruptures  the  antrum  fills  with 
blood  and  forms  the  corpus  hemorrhagicum.  This  body 
becomes  organized  and  the  hemoglobin  is  absorbed, 
which  leaves  a  yellowish  body,  due  to  the  presence 
of  many  large  yellow  cells  called  lutein  cells.  The 
corpus  luteum  occurs  every  twenty-eight  days.  If 
fecundation  occurs  the  corpus  luteum  persists  in  the 
ovum  as  a  yellowish  body  as  described  above,  and 
persists  throughout  the  term  of  pregnancy.  How- 
ever, if  fecundation  does  not  occur  the  corpus  luteum 
shortly  contracts,  becomes  whitish  and  forms  the  corpus 
albicans. 

The  latter  change  is  supposed  to  be  due  to  a  fatty 
degeneration  of  the  lutein  cells.  The  corpus  luteum 
is  considered  a  periodic  self-developing  gland  with  an 
internal  secretion.  Ovulation  and  menstruation  have 
a  close  relationship.  Menstruation  signifies  a  frus- 
trated ovulation  and  the  discharge  of  a  hyperemic 
membrane  from  the  uterus.     Rupture  of  the  Graafian 


THE  INTERNAL  ORGANS  OF  REPRODUCTION      427 

follicle  occurs  on  an  average  nine  days  in  advance  of 
the  bleeding.^  While  the  ovum  is  moving  along  the 
tube  the  transformation  of  the  membrana  granulosa, 
of  the  ruptured  Graafian  follicle,  to  the  corpus  luteum 
is  taking  place.  The  tenth  day  before  menstruation 
is  the  surest  time  for  impregnation. 

There  are  many  theories  on  the  above  which  are  not 
mentioned  as  they  are  beyond  the  scope  of  this  book. 

Menstruation. — This  is  a  process  characterized  by  a 
discharge  of  blood  from  the  vagina,  which  takes  place 
periodically,  except  during  pregnancy  and  lactation, 
when  the  mammary  glands  are  secreting  milk.  It 
occurs  from  the  time  of  puberty  to  the  menopause 
(change  of  live).  Ordinarily  it  comes  on  every  four 
weeks  and  lasts  from  three  to  five  days.  It  varies 
as  to  frequency  and  duration  in  different  individuals. 

The  age  at  which  the  menses  (periodic  sickness) 
commences,  varies  in  different  countries,  being  earlier 
in  warm  and  later  in  cold  climates.  The  average  age 
in  a  temperate  climate  is  about  the  fourteenth  to 
fifteenth  year. 

There  have  been  several  theories  expressed  in 
regard  to  the  changes  taking  place  in  the  mucous 
membrane  of  the  uterus  at  the  time  of  menstruation. 
Some  authorities  claim  that  the  entire  mucous  mem- 
brane of  the  uterus  is  broken  down  and  thrown  off  in 
the  menstrual  flow.  Again,  others  claim  that  there  is 
no  destruction  of  tissue,  and  the  menses  results  from 
a  thickening  of  the  mucous  membrane  of  the  uterus 
(womb),  engorgement  of  its  superficial  bloodvessels, 
followed  by  the  escape  of  blood,  due  in  part  to  the 
rupturing  of  these  vessels,  and  the  passing  of  blood 
through  the  walls  of  the  arteries  (diapedesis).  Follow- 
ing the  period  of  hemorrhage  a  certain  amount  of 
degeneration  of  the  cells  takes  place  in  the  mucous 


1  The  above  facts  as  per  Dr.  Miller,  Berliner  klinische  Wochen- 

schrift,  May  5,  1913;   N.  Y.  Med.  Journal. 


428  ORGANS  OF  REPRODUCTION 

membrane  of  the  uterus,  which  is  followed  by  a  period 
of  repair  when  an  entirely  new  membrane  is  formed. 
Thus  the  changes  taking  place  in  the  uterus  during 
menstruation  last  for  several  days  (sixteen)  as  follows: 
Five  days  for  engorgement  of  the  membrane,  four 
days  for  the  bleeding  or  menses  proper,  and  seven  days 
for  the  repair  of  the  membrane  after  the  bleeding  stops. 
The  menopause  is  the  term  given  to  the  cessation 
of  the  menstrual  flow.  It  occurs  usually  at  about  the 
forty-fifth  year.  Cases  have  been  reported  where  it 
has  stopped  as  early  as  the  twenty-eighth  or  thirtieth 
year,  and  extended  on  the  other  extreme  to  the  fiftieth 
year. 

QUESTIONS 

1.  How  long  is  the  female  urethra? 

2.  Where  does  it  open  and  what  organ  does  it  empty  during 
micturition? 

3.  Name  the  internal  organs  of  reproduction. 

4.  Give  the  location  of  the  uterus.     Its  dimensions. 

5.  Name  the  portions  of  the  uterus. 

6.  What  structures  open  into  the  cavity  of  the  uterus  at  the 
superior  angles? 

7.  Into  what  does  the  cervix  of  the  uterus  open? 

8.  What  forms  the  wall  of  the  uterus? 

9.  What  type  of  epithelium  lines  the  body  of  the  uterus? 

10.  Name  the  ligaments  of  the  uterus. 

11.  What  structures  are  found  between  the  layers  of  the  broad 
ligament? 

12.  How  long  are  the  Fallopian  tubes? 

13.  What  coats  form  their  walls? 

14.  Does  the  Fallopian  tube  communicate  with  the  cavity  of  the 
uterus?    The  peritoneal  cavity? 

15.  What  variety  of  epithelium  is  found  in  the  mucous  membrane 
of  the  Fallopian  tube? 

16.  What  cell  is  produced    in    the    ovary   which   represents   the 
female  portion  of  reproduction? 

17.  Where  are  the  ovaries  located?     Give  dimensions,  weight. 

18.  What  structure  is   attached   to   the   outer  extremity   of   the 
ovary? 

19.  Describe  a  Graafian  follicle.    Give  contents. 

20.  From  which  group  of  cells  in  the  Graafian  follicle  is  the  ovum 
or  germ  cell  developed? 

21.  What  must  fertilize  the  ovum  to  reproduce  the  offspring? 

22.  What  do  you  understand  by  ovulation?     How  often  does  it 
occur? 

23.  How  does  a  mature  ovum  reach  the  cavity  of  the  uterus? 


TABLES  OF  WEIGHTS  AND  MEASURES 


Symbols  and  Abbreviations  for  Apothecaries'  or  Troy 
Weights 

gr.,  Granurn.     A  grain. 
3,  Scrupulus.     A  scruple,  equal  to  20  grains. 
3,  Drachma.     A  drachm,  equal  to  60  grains. 
5,  Uncia.     An  ounce,  equal  to  480  grains, 
lb.  Libra.     A  pound  of  12  ounces  of  480  grains  each. 


Table  of  Troy  or  Apothecaries'  Weights 

20  grs.   =13. 
60  grs.   =  1  3  or  3  3. 
8      3=15. 
12     5=1  ib. 


Symbols  and  Abbreviations  for  Apothecaries'  or  Wine 
Measures 

gtt,  Gutta.     A  drop. 
TTl,  Minimum.     A  minim  is  the  sixtieth  part  of  a  fiuidrachm. 
f3,  Fluidrachma.     A  fiuidrachm  is  the  eighth  part  of  a  fluid 

ounce  or  60  minims. 
f3 ,  Fluiduncia.     A  fluidounce,  equal  to  480  minims  or  sixteentli 

of  a  pint. 
O,  Octarius.     A  pint  of  16  fiuidounces. 
Cong.,  Congius.     A  gallon  of  8  pints  or  128  fiuidounces. 
83,  means  half,  as  3ss,  |  drachm. 

Table  of  Wine  or  Apothecaries'  Measures 

meo  =  f3j. 

f3   8  =  f5j  or  480  minims. 

f516  =    Oj. 

02  =    1  quart  or  f532. 

08  =    1  cong.  gallon. 

1  teaspoonful  =  f3j- 

1  dessertspoonful  =  f3ij- 

1  tablespoonful  =  i^sa  or  f3iv. 

Wineglass  =  fSJ- 

Teacup  =  f5iv. 


GLOSSARY 


Abdomen.  (From  the  Latin  word  abdere,  "to  hide.")  The  portion 
of  the  body  included  between  the  thorax  and  pelvis,  which  contains 
the  stomach,  liver,  spleen,  kidneys,  etc. 

Abducens.  A  nerve  to  the  external  rectus  muscle  of  the  eye,  which 
abducts  it. 

Abduction.  (From  the  Latin  word  ab,  "from;"  ducere,  "to  lead.") 
The  withdrawal  of  a  part  from  the  axis  of  the  body,  organ,  or  limb. 

Abductor.  Muscles  which  draw  the  part  away  from  the  axis  of  the 
body,  organ,  or  limb. 

Abductor  Hallucis.    Abductor  of  the  big  toe.    See  Hallux. 

Abductor  Minimi  Digiti.    Abductor  of  the  little  toe  or  finger. 

Abductor  Pollicis.    Abductor  of  the  thumb.     See  Pollicis. 

Absorption.  (From  the  Latin  word  absorbere,  "to  suck  in.")  The 
passage  from  without  into  the  capillary  or  lymphatic  vessels  of  nutri- 
tive or  waste  materials  from  the  tissues. 

Accessorius.  (Flexor  muscle.)  Aids  the  flexor  longus  digitorum 
muscle  to  contract.    The  lumbricales  are  also  called  accessory  muscles. 

Accessory.  (From  the  Latin  word  accessorius.)  Aiding  in  pro- 
ducing some  effect,  as  an  auxiliarj^,  to  muscles,  glands,  nerves,  etc. 

Acetabulum.  (From  the  Latin  word  acetabulum,  "a  little  cup  for 
holding  vinegar  [acetum].") 

Acid  in  Reaction.  Is  a  term  used  to  express  the  response  to  a  certain 
test  (litmus  paper),  as  to  the  acidity  of  a  clinical  solution,  secretion, 
excretion  from  the  body,  or  any  of  its  organs,  membranes,  etc. 

Acromial  (process).    Pertaining  to  the  acromion. 

Acromion.  (From  the  Greek  words  meaning  summit,  shoulder.) 
The  outtn'  extremity  of  the  spine  of  the  scapula. 

Adductors.  Muscles  which  draw  the  part  toward  the  axis  of  the 
body,  organ,  or  limb. 

Adductor  Brevis.    The  short  adductor  (thigh). 

Adductor  Longus.    The  long  adductor  (thigh). 

Adductor  Magnus.    The  large  adductor  (thigh). 

Adductor  Obliquus  Hallucis.  The  oblique  adductor  of  the  big  toe. 
See  Hallux. 

Adductor  Obliquus  Pollicis.  The  oblique  adductor  of  the  thumb. 
See  Pollicis. 

Adductor  Transversus  Hallucis.  The  transverse  adductor  of  the 
big  toe. 

Adductor  Transversus  Pollicis.  The  transverse  adductor  of  the 
thumb. 


432  GLOSSARY 

Adduction.  (From  the  Latin  words  ad,  "to;"  ducere,  "to  lead.") 
The  drawing  of  a  part  toward  the  axis  of  the  body,  organ,  or  limb. 

Adenoid.    Resembling  a  gland,  as  glandular  tissue. 

Adipose  (Tissue).     (From  the  Latin  word  adeps,  "fat.")    Fatty. 

AdrenaL  (From  the  Latin  words  ad,  "near  to;"  ren,  "the  kidney.") 
Adjacent  to  the  kidney. 

Adventitia.  (From  the  Latin  word  adventitius,  "foreign.")  The 
outer  coat  of  a  bloodvessel. 

Afferent.  (From  the  Latin  word  afferens,  "carrying  to.")  Carrying 
to  the  centre.  Sensor  nerves  conveying  impulses  from  the  periphery 
to  the  ganglia  of  the  spinal  cord,  and  to  the  centres  in  the  brain. 

Alkaline  in  Reaction.  Is  a  term  used  to  express  the  response  to  a 
certain  test  (litmus-paper),  as  to  the  alkalinity  of  a  chemical  solution, 
secretion,  or  excretion  from  the  body  or  any  of  its  organs,  membranes, etc. 

Alveolar.  (From  the  Latin  word  alveolus,  "a  small  hollow.")  Per- 
taining to  an  alveolus. 

Alveolus  (pi.  i).  A  small  hollow.  As  the  spaces  in  the  lungs  at 
the  end  of  the  bronchioles. 

Ameba.  (From  the  Greek  word  ameibo,  "to  change.")  A  colorless, 
single-celled,  jelly-like,  protoplasmic  organism  found  in  sea  and  fresh 
waters,  constantly  undergoing  changes  of  form  and  nourishing  itself 
by  englobing  surrounding  objects. 

Ameboid.  Resembling  an  ameba  in  its  movements.  As  a  white 
cell  of  the  blood. 

Amphiarthrosis.  (Around  a  joint.)  A  mixed  articulation  permitting 
slight  motion. 

Ampulla  (Vater).  (From  the  Latin  word  meaning  a  narrow-necked 
vessel  shaped  like  a  jug,  in  which  the  ancient  Romans  conveyed  jellies 
or  ointments) .  A  portion  of  the  membrane  of  the  duodenum  where  the 
common  bile  duct  and  pancreatic  duct  open.  Ampulla,  any  space 
shaped  as  above. 

Amyelinic.    Without  a  myelin  sheath. 

Amylose.  (From  the  Greek  word  meaning  starch.)  Any  one  of 
the  group  of  carbohydrates,  comprising  starch,  glycogen,  dextrin. 

Anabolism.  Constructive  metabolism.  Activity  and  repair  of 
function  by  the  tissues,  opposed  to  katabolism. 

Anastomose.  To  communicate  with  each  other,  as  arteries,  veins, 
lymphatics,  etc. 

Anastomosis.  The  communication  between  arteries,  veins,  and 
lymphatics  within  the  skin,  muscles,  organs,  etc. 

Anatomic.    Relating  or  belonging  to  anatomy. 

Annular  (ligament).  (From  the  Latin  word  annulus,  "a  ring.") 
Ring-like.    The  ligament  surrounding  the  wrist  and  ankle. 

Annulus  Ovalis.  "The  oval  ring."  The  oval  margin  of  the  foramen 
ovale  in  the  interauricular  wall  of  the  heart.  (Ovalis  from  the  Latin 
word  ovum,  "an  egg.") 

Antebrachium.  (From  the  Latin  word  ante,  "before";  brachium, 
"arm.")    The  forearm. 

Antecubital.    The  a  space  in  front  of  the  elbow-joint. 

Anterior.  Perforated  space.  An  irregular  quadrate  space,  situated 
at  the  inferior  surface  of  the  cerebrum,  between  the  olfactory  trigone 
and  the  optic  chiasm  and  tract. 


GLOSSARY  433 

Antr^n  (Highmore).  A  hollow  cavity  found  in  each  maxilla  bone. 
The  aiimim:    any  hollow  cavity  or  space. 

Apex.    The  tip,  point,  or  extremity  of  anything. 

Aponeurosis.  A  fibrous,  membranous  expansion  of  a  tendon  giving 
attachment  to  muscles  or  serving  to  enclose  and  bind  down  muscles. 

Appendicular.  (From  the  Latin  word  appendicula,  "a  small  appen- 
dix.   See  Appendix.)    Pertaining  to  the  extremities  of  the  body. 

Appendix  (vermiform).  (From  the  Latin  word  appendere,  'Ho  hang 
upon  or  to.")    An  appendage. 

Aqueductus.  (From  the  Latin  words  aqua,  "water;"  ductus,  "a 
leading.")  Any  canal  for  the  passage  of  fluid.  Nerves,  arteries,  etc., 
in  structures  of  the  body. 

Aqueous.  (From  the  Latin  word  aqua,  "water.")  Watery,  as  the 
aqueous  humor  within  the  eye-ball. 

Arachnoid.  Resembhng  a  spider's  web.  A  membrane  of  the  spinal 
cord  and  brain  between  the  pia  and  dura  mater. 

Arbor  Vitae.  (From  the  Latin  words  arbor,  "a  tree;"  vitae,  "of 
life.")  The  appearance  of  a  structure  resembling  the  evergreen  tree; 
as  seen  on  cutting  the  cerebellum  in  a  longitudinal  section,  also  the 
similar  appearance  of  the  folds  of  the  mucous  membrane  of  the  neck 
of  the  uterus. 

Areolar.  (From  the  Latin  word  areola,  dim.  of  area,  "an  open 
space.")  Relating  to  areola  (pi.  ae).  Any  minute  space  in  a  tissue, 
as  seen  in  cellular  or  loose  connective  tissue. 

Artefact.  (From  the  Latin  words  arte,  "by  art;"  factum,  "made.") 
A  structure  or  tissue  which  has  been  changed  from  its  natural  state. 
(Can  only  be  seen  by  the  microscope.) 

Arteriole.  (From  the  Latin  word  arteriola,  a  small  artery.)  A  very 
small  artery  continued  from  the  larger  arteries  and  ends  in  the  capillary. 

Artery.  (From  the  Greek  meaning  "to  keep  air."  The  ancients 
always  though  the  arteries  contained  air.)  A  closed  tube  which  con- 
veys the  blood,  propelled  by  the  heart,  to  all  parts  of  the  body  and 
terminates  as  the  arterioles  and  capillaries. 

Arthrosis.  (From  the  Greek  meaning  "to  fasten  by  a  joint.") 
Articulation  or  jointing,  as  the  extremities  of  bones  are  joined  by 
ligaments. 

Articular.  (From  the  Latin  word  articularis,  "of  the  joint.") 
Pertaining  to  an  articulation  or  joint. 

Arjrtenoid,    Resembling  the  mouth  of  a  pitcher. 

Asternal.    Not  connected  with  the  sternum,  as  the  false  ribs. 

Astragalus.  (Named  from  the  Greek  meaning  a  dice,  named  from 
the  fact  that  the  ancients  used  the  corresponding  bones  of  the  sheep 
as  dice.)    The  ankle  bone  upon  which  the  tibia  rests. 

Atlas.  The  first  vertebra  of  the  spinal  column  articulating  with  the 
occipital  bone  and  thus  sustaining  the  globe  of  the  head,  whence  the 
name.  (Any  support  or  prop  is  termed  an  atlas,  based  on  the  belief 
of  the  ancient  Greeks  that  the  gods  (Atlantes)  bore  up  the  pillars  of 
heaven,  which  were  named  after  Mount  Atlas  in  Western  Africa.) 

Atrioventricidar.  Relating  to  both  the  atrium  (auricle)  and  ventricle 
of  the  heart. 

Atrium,     (The  forecourt  or  hall.)     That  part  of  the  auricle  of  the 
heart  into  which  the  venous  blood  is  poured. 
28 


434  GLOSSARY 

Auriculo ventricular.  (From  the  Latin  words  auricula,  "ear;"  ven- 
triculus,  "ventricle.")  Relating  to  an  auricle  and  ventricle  of  the 
heart. 

Axial.  (From  the  Latin  word  axis,  see  Axis.)  Pertaining  to  the 
centre  or  situated  in  an  axis. 

Axilla.    The  arm-pit. 

Axillary.    Pertaining  to  the  axilla. 

Axis.  (From  the  Latin  word  axis,  "an  axletree.")  An  imaginary 
line  passing  through  the  centre  of  a  body.  The  second  cervical  ver- 
tebra Arterial  axis:  A  short  artery  which  breaks  up  into  several 
branches. 

Axone  or  Axis-cylinder.  (From  the  Latin  axis,  "an  axletree.")  The 
essential  part  of  a  nerve  cell  which  conducts  nerve  impulses. 

Basilar.    Pertaining  to  the  base. 

Basilic  (vein).  (From  the  Greek  meaning  royal.)  Eminent,  illus- 
trious.   The  large  vein  on  the  inner  side  of  the  arm. 

Biceps  (muscle).  (From  the  Latin  words  bis,  "twice;"  caput, 
"head.")    Having  two  heads. 

Brachialis  Anticus  (muscle).    In  front  of  the  arm. 

Brachiocephalic  (artery  and  vein).  Pertaining  to  the  arm  and 
head. 

Bronchial.     Relating  to  the  bronchus. 

Bronchiole.  (Dim.  of  bronchus.)  One  of  the  smallest  subdivisions 
of  a  bronchus. 

Bronchus  (pi.  i).  (From  the  Greek  meaning  windpipe.)  One  of 
the  primary  divisions  of  the  trachea. 

Buccal.  (From  the  Latin  word  bucca,  "cheek.")  Pertaining  to 
the  cheek. 

Buccinator  (muscle).  From  the  Latin  word  buccinare,  "to  blow 
the  trumpet.")    So  called  from  its  use  in  blowing  the  trumpet,  etc. 

Bursa.  (From  the  Latin  word  "purse.")  A  small  sac  interposed 
between  parts  that  move  upon  one  another. 

Bursal.    Pertaining  to  bursa. 

Bifid.  (From  the  Latin  words  bis,  "twice;"  findere,  "to  cleave.") 
Divided  into  two  parts. 

Bipolar.  (From  the  Latin  words  bi,  "two;"  polus,  a  "pole"). 
Having  two  poles.  Nerve  cells  having  two  prolongations  of  their 
cell  matter  are  termed  bipolar. 

Blastodermic  Vesicle.  Pertains  to  the  blastoderm.  (The  germinal 
membrane  formed  by  the  cells  of  the  morula  or  mulberry  mass,  lying 
on  the  internal  surface  of  the  vitelline  membrane  of  the  impregnated 
ovum.) 

Blastula.    The  blastodermic  vesicle. 

Brachial  (artery).  (From  the  Latin  word  brachium,  "arm.")  Per- 
taining to  the  arm.  B.  artery:  continuation  of  the  axillary  artery  in 
the  arm. 

Brachium.  (From  the  Latin  word  brachium,  "arm.")  The  arm, 
from  the  shoulder  to  elbow. 

Calcaneum  (bone).  (From  the  Latin  word  calx,  "a  heel.")  The 
bone  of  the  heel,  also  os  calcis. 

Calices  (pi.  of  Calix).  (From  the  Latin  word  calix,  "a  cup  or 
chalice.")    Cup-like  depressions  of  the  membrane  of  the  pelvis  of  the 


GLOSSARY  435 

ureter  which  surround  and  collect  the  urine  from  the  papilla  of  the 
kidney. 

Canaliculus.  (From  the  Latin  word  canaliculus,  "a  small  channel  or 
canal.")  Any  one  of  the  minute  canals  opening  into  the  lacunae 
(lakes)  of  bones. 

Cancellous.  (From  the  Latin  word  cancelli,  "lattice-work.")  Re- 
sembling lattice-work,  as  the  tissue  in  the  articular  ends  of  long  bones. 

Capillary.  (From  the  Latin  word  capillus,  "a  hair.")  Hair-like. 
A  minute  bloodvessel  connecting  the  arterioles  and  venules. 

Capitellum.  (Dim.  of  the  Latin  word  caput,  "a  head.")  A  small 
head. 

Carbon  Dioxide.  An  acid,  gaseous  product  having  the  composition 
of  one  atom  of  carbon  to  two  of  oxygen  (CO2).  It  is  formed  in  the 
tissues  as  a  result  of  metabolism.  When  inhaled  or  accumulated 
in  the  tissues  in  excess  it  will  destroy  animal  life  by  asphyxiation.  It 
kills  by  depressing  the  respiratory  centre. 

Cardiac.    Pertaining  to  the  heart  or  the  cardia  of  the  stomach. 

Carpus.    The  wrist.    Eight  bones  collectively  form  it. 

Cava  Vena.  (From  the  Latin  words  cavus,  "sl  hollow;"  vena, 
"a  vein.")  The  large  veins  which  open  and  empty  venous  blood 
into  the  right  auricle  of  the  heart  from  the  systemic  veins. 

Cavernous  (sinus).  (Caverna,  a  cave.)  Having  hollow  spaces. 
The  venous  sinus  at  the  sides  of  the  body  of  the  sphenoid  bone.  It 
lodges  the  carotid  artery  and  its  sheath,  and  nerves  to  the  eye  muscles. 

Celiac.    Pertaining  to  the  belly. 

Cellular.  (From  the  Latin  word  cella,  "a  cell.")  Pertaining  to  or 
composed  of  cells. 

Centrifugal.  (From  the  Latin  words  centrum,  "to  centre;"  fugere, 
to  fly,")  Receding  from  the  centre  to  the  periphery.  C.  nerve:  One 
which  conducts  impulses  from  the  brain  and  spinal  cord  to  the  periphery. 

Centripetal.  (From  the  Latin  word  centrum,  "centre;"  petere, 
"to  seek.")  TraveUng  from  the  periphery  toward  the  centre.  C. 
nerve:  One  which  conveys  impulses  from  the  periphery  toward  the 
brain  and  spinal  cord. 

Cephalic.    Pertaining  to  the  head. 

Cerebellar.     (Dim.  of  cerebrum.)    Pertaining  to  the  cerebellum. 

Cerebellum.  (Dim.  of  cerebrum.)  The  lower  part  of  the  brain 
lying  below  the  cerebrum  and  above  the  pons  and  medulla. 

Cerebral.    Pertaining  to  the  cerebrum. 

Cerebrum.  (From  the  Latin  word  cerebrum,  "brain.")  The  chief 
portion  of  the  brain. 

Cervical.  (From  the  Latin  word  cervix,  "a  neck.")  Pertaining 
to  the  neck — of  the  body,  organ,  etc. 

Cervix.    A  neck,  or  constricted  portion. 

Chemic  or  Chemical.    Of  or  pertaining  to  chemistry. 

Chiasm  (optic).  (From  the  Greek  meaning  "to  make  a  cross,  as 
an  X.")  The  optic  commissure,  where  the  fibers  of  the  optic  nerves 
meet  and  cross  to  pass  to  the  optic  tracts. 

Chondroblast.    A  cell  of  developing  cartilage. 

Chordae  Tendineae.  Tendinous  strings,  which  are  attached  by 
their  two  ends  to  the  papillary  muscles  and  margins  of  the  auriculo- 
ventricular  valves  in  the  ventricles  of  the  heart. 


436  GLOSSARY 

Chromatin.  (From  the  Greek  word  meaning  color.)  The  portion 
of  the  protoplasm  of  a  cell  which  takes  the  stain;  forming  a  delicate 
net-work  of  fibrils  permeating  the  achromatin  of  a  cell.  Achromatin: 
The  opposite  of  chromatin. 

Chyle.  The  milk-white  fluid  absorbed  by  the  lacteals  during 
digestion. 

Chsone.  Food  that  has  undergone  gastric  digestion  and  has  not 
been  acted  upon  by  the  bile,  pancreatic,  and  intestinal  secretions. 

Cilia.  (From  the  Latin  word  cilium,  *'an  eyelash.")  The  eye- 
lashes. The  hair-like  appendages  of  certain  epithelial  cells,  the  func- 
tion of  which  is  to  propel  fluid  or  secretion. 

Ciliary.    Pertaining  to  the  eyelash.    Relating  to  ciliary  movement. 

Ciliated.    Having  cilia. 

Circumduction.  (From  the  Latin  words  circum,  "around;"  ducere, 
"to  lead.")  The  movement  of  a  limb  in  such  a  manner  that  its 
extremity  describes  a  circle,  the  nearest  end  being  fixed. 

Clavicle.    (From  the  Latin  word  clavus,  "a  key.")    The  collar-bone 

Clinoid.  (From  the  Greek  meaning  beet-like.)  Resembling  a  beet. 
The  clinoid  processes  of  the  sphenoid  bone. 

Coagulation.  (From  the  Latin  word  coagulatio,  "sb  clotting.") 
The  formation  of  a  clot  as  in  blood  or  milk. 

Coaptation.    The  adjustment  of  parts  to  each  other. 

Coccyx.  (From  the  Greek  word  meaning  a  cuckoo,  resembling  the 
bill.)    The  last  bone  of  the  vertebral  column. 

Cochlea.  The  cavity  of  the  internal  ear,  which  resembles  a  snail 
shell. 

Coeliac.     (See  Celiac.) 

Coitus.  (From  the  Latin  word  coitio,  "a  going  together.")  The 
act  of  sexual  connection. 

Collateral.  (From  the  Latin  words  con,  "together;"  laterahs,  "of 
the  side.")    Accessory  or  secondary. 

Columnae  Cameae  (heart).  (Lt.,  the  fleshy  columns.)  The  mus- 
cular columns  projecting  from  the  inner  surface  of  the  ventricles  of 
the  heart. 

Columnae  Rugarum  (vagina).  (From  the  Latin  word  columnae, 
"columns;"  rugarum,  "of  the  folds  or  ridges.")    The  columns  of  ridges. 

Commissure.  (From  the  Latin  words  com,  "together;"  mittere,  "to 
send.")    That  which  unites  two  parts. 

Compressor  Narium  Minor.    The  small  compressor  of  the  nostrils. 

Compressor  Nasi.    The  compressor  of  the  nose. 

Concave.  (From  the  Latin  words  con,  "together;"  cavus,  "hollow.") 
Hollow,  incurved,  as  the  inner  surface  of  a  hollow  sphere. 

Condyle.  (From  the  Greek  word  meaning  a  knuckle).  -'Any  rounded 
eminence  such  as  occurs  in  the  joints  or  parts  of  many  of  the  bones. 

Condyloid.     Resembling  a  condyle. 

Connective.    To  connect;  as  C.  tissue. 

Contiguous.  (From  the  Latin  word  contiguus  from  the  verb  con- 
tingere,  "to  touch;"  as  it  were,  on  all  sides.)  In  actual  or  close 
contact;  touching;  adjacent 

^^  Conus  Arteriosus  (heart).  From  the  Latin  word  conus,  "a  cone.") 
The  arterial  cone.  The  cone-shaped  eminence  of  the  right  ventricle 
of  the  heart,  whence  arises  the  pulmonary  artery. 


GLOSSARY  437 

Convex.  (From  the  Latin  words  com,  "together,"  vehere  "to 
carry.")     Elevated  and  regularly  rounded. 

Coracoid.  (From  the  Greek  words  meaning  "the  likeness,  a  crow.") 
Resembling  a  crow's  beak. 

Cornicula  Laryngis.  Little  horn  of  the  larynx,  cartilage  of  larynx 
Santorini,  named  after  the  man  who  described  it  first,  Santorini. 

Cornua.  (From  the  Latin  word  cornu,  "a  horn.")  A  name  applied 
to  any  excrescence  resembling  a  horn. 

Coronal.  (From  the  Latin  word  corona,  "a  crown.")  Encircling 
like  a  crown,  pertaining  to  the  crown  of  the  head. 

Coronoid.    Resembling  a  crown. 

Corporeal.  (From  the  Latin  word  corporeus,  from  corpus,  "a 
body.")  Having  a  body.  Pertaining  to  the  body.  C.  circulation:  of 
the  body. 

Corpus  Callosum.  (From  the  Latin  word  corpus,  "a  body;"  callosus, 
from  callus,  "callous  or  hard-skinned.")  The  callous  body.  The 
broad  band  of  white  matter  connecting  the  two  hemispheres  of  the 
cerebrum. 

Corpuscle.     (Dim.  of  corpus,  "a  body.")    A  small  body. 

Corpus  Hemorrhagicum.  The  hemorrhagic  body,  formed  when  the 
bloodvessels  of  the  Graafian  follicle  rupture  after  the  escape  of  the 
ovum. 

Corrugator  Supercilii  (muscle).    The  wrinkler  of  the  eyebrow. 

Cortex.  (From  the  Latin  word  cortex,  "bark.")  The  bark  of  a 
tree,  hence  the  outer  covering,  as  the  cortex  cerebri,  covering  of  the 
cerebrum;  cortex  renalis,  covering  of  the  kidney;  The  outer  portion 
of  an  organ  is  called  the  cortex, 

Costa  (pi.  se).     (From  the  Latin  word  costa,  "a  rib.")    The  rib. 

Costal.    Pertaining  to  the  rib. 
"•    Cranium.     (From  the  Greek  word  meaning  cranium).     The  bony 
cavity  that  contains  the  brain,  its  membranes  and  vessels. 

Cribriform.  (From  the  Latin  word  cribrum,  "a  sieve;"  forma, 
"form.";    Perforated  like  a  sieve. 

Cricoid.    Ring-shaped. 

Cricothyroid.    Pertaining  to  the  cricoid  and  thyroid  cartilages. 

Crista  (GalK).  (From  the  Latin  word  crista,  "crest.")  The  crista 
galli;  cock's  crest. 

Crucial.  (From  the  Latin  word  crux,  "a  cross.")  Resembling  a 
cross. 

Crura  Cerebri.  (The  legs  of  the  cerebrum.)  The  peduncles  of  the 
cerebrum  which  connect  it  with  the  pons  Crura  cerebelli;  any  one  of 
the  cerebellar  peduncles. 

Crus  (pi.  crura).     (From  the  Latin  word  crus,  "a  leg,  support.") 

Cubic  Centimeter  (c.c).  Is  the  unit  of  measurement  used  in  the 
metric  system  for  fluids  in  place  of  the  gram;  one  cubic  centimeter 
representing  1  fluid  gram. 

Cuboid.    Resembling  a  cube. 

Cuboidal.    Nearly  like  the  shape  of  a  cube. 

Cuneiform.  From  the  Latin  words  cuneus,  "a  wedge;"  forma, 
"shape.")     Wedge-shaped. 

Cutaneous.  (From  the  Latin  word  cutis,  "skin.")  Pertaining  to 
the  skin. 


438  GLOSSARY 

Cuticle.     (Dim.  of  cutis.)    The  epidermis  (upper  layer  of  skin). 

Cutis  (skin).    The  derma  or  true  skin. 

Cyanotic.  Referring  to  cyanosis  (a  bluish  discoloration  of  the  skin 
and  lips  from  deficient  oxidation  of  the  blood,  caused  by  local  or 
general  circulatory  disturbance). 

Cylindrical.    Having  the  form  of  a  cylinder. 

Cystic.  (From  the  Greek  word  meaning  a  pouch).  Pertaining  to 
or  resembling  a  pouch.    Pertaining  to  the  gall-bladder. 

Deciduous.  (From  the  Latin  words  de,  ''from;"  cadere,  "to  fall.) 
Falling  off.    The  deciduous  teeth;  temporary  or  milk  teeth. 

Decussate.  (From  the  Latin  word  decussatus,  "crossed.")  To 
intersect,  to  cross. 

Decussation.  (From  the  Latin  word  decussatio,  a  crossing.)  An 
X-shape  crossing,  especially  of  symmetric  parts,  as  of  nerve  fibers, 
nerve  tracts.  The  chief  decussations  are  that  of  the  optic  nerves  in  the 
chiasm,  and  that  of  the  crossed  pyramidal  tracts  in  the  medulla. 

Defecation.    The  evacuation  of  the  bowels. 

Deglutition.  (From  the  Latin  word  deglutitio,  "a  swallowing.") 
The  act  of  swallowing,  food,  water,  etc. 

Deltoid  (muscle).  Having  the  shape  of  the  Greek  letter  Delta,  A; 
triangular. 

Dendraxones.    Branching  in  appearance,  like  a  tree. 

Dendrite.  (From  the  Greek  word  meaning  a  tree.)  Branching 
like  a  tree.  The  processes  of  a  nerve  cell  or  neurone  which  increases 
its  functional  surface  for  the  conduction  of  nerve  impulses. 

Dentations.  Resembling  the  form  of  a  tooth,  as  a  toothed  or  serrated 
edge. 

Dentoplasm.    A  tooth-like  arrangement  of  the  plasma. 

Depressors.  (From  the  Latin  word  deprimere,  "to  depress.")  A 
group  of  muscles  which  depress  or  lower  any  bone  or  organs  by  their 
contractions. 

Depressor  Alas  Nasi.    Depressor  of  the  wing  of  the  nose. 

Depressor  Anguli  Oris.    Depressor  of  the  angle  of  the  mouth. 

Depressor  Labii  Inferioris.    Depressor  of  the  lower  lip.  ^ 

Derma.      (From  the  Greek  word  meaning  the  skin.)     The  true  skin. 

Dextroses.  (From  the  Latin  word  dexter,  "right.")  A  group  of 
sugars  that  rotate  polarized  light  to  the  right. 

Dialysis.  The  separation  of  several  substances  from  each  other  in 
solution  by  taking  advantage  of  their  different  diffusibility  through 
porous  membranes.  Those  that  pass  through  readily  are  termed 
crystalloids,  those  that  do  not  colloids. 

Diaphragm.  (From  the  Greek  words  meaning  across  and  wall.) 
The  musculomembranous  partition  which  separates  the  thorax  from 
the  abdomen. 

Diapedesis.  The  passage  of  the  blood  through  the  unruptured 
vessel  wall. 

Diarthrosis.  The  connection  of  two  bones  admitting  of  free  motion 
between  them,  as  at  the  articulations. 

Diastole.  (From  the  Greek  word  meaning  a  drawing  apart  )  The 
period  of  dilatation  of  a  chamber  of  the  heart. 

Diffuse.    Scattered;  not  limited  to  one  tissue  or  spot. 

Digastric  (muscle).    Having  two  bellies. 


GLOSSARY  '  439 

Digestion.  (From  the  Latin  word  digerere,  "to  digest.")  Those 
processes  whereby  the  food  taken  into  the  aUmentary  canal  is  made 
capable  of  being  absorbed  and  assimilated  by  the  tissues. 

Dilator  Naris  Anterior  (muscle).    Anterior  dilator  of  the  nostril. 

Dilator  Naris  Posterior  (muscle).     Posterior  dilator  of  the  nostril. 

Diploblast.  (From  the  Greek  words  meaning  double  sprout.) 
Formed  of  two  layers. 

Diploe.  (From  the  Greek  word  meaning  a  fold.)  The  cancellous 
bony  tissue  between  the  outer  and  inner  tables  of  the  skull. 

Disintegration.  (From  the  Latin  words  dis,  "apart;  "integer, 
the  whole.")    The  act  of  breaking  up  or  decomposing. 

Distal.  (From  the  Latin  word  distare,  "to  be  at  a  distance.") 
Extreme;  at  the  greatest  distance  from  a  central  point. 

Diverging.    To  proceed  from  a  common  point  in  different  directions. 

Dorsal.  (From  the  Latin  word  dorsum,  "back.")  Pertaining  to 
the  back  of  the  body  or  organ,  etc. 

Dorsalis  Pedis.    The  back  of  the  foot. 

Dorsum.  The  back  or  posterior  of  the  body,  organ,  etc.  (See 
Dorsal.) 

Duct.  (From  the  Latin  word  ducere,  "to  lead.")  A  tube  or  channel, 
especially  one  for  conveying  the  secretions  of  a  gland. 

Ductus  Arteriosus.  A  short  vessel  in  the  fetus  connecting  the 
pulmonary  artery  with  the  aorta. 

Ductus  Communicus  Choledochus.     The  common  bile  duct. 
(Literally,  the  duct  which  receives  the  bile.)     The  common  excretory 
duct  of  the  Hver  and  gall-bladder. 

Ductus  Venosus.  A  branch  of  the  umbilical  vein  in  the  fetus  which 
empties  directly  into  the  ascending  vena  cava. 

Duodenum.  (From  the  Latin  word  duodeni,  "twelve  each."  So 
called  because  it  is  about  twelve  finger-breadths  in  length.)  The 
first  part  of  the  small  intestine  . 

Dura  Mater.  (From  the  Latin  words  dura,  "hard;"  mater, 
"mother.")  The  fibrous  membrane  forming  the  outer  covering  of  the 
brain  and  spinal  cord. 

Ectoderm.  (From  the  Greek  words  meaning  outside,  the  skin.) 
The  outer  of  the  two  primitive  layers  of  the  blastodermic  vesicle  in 
the  embryo. 

Edema.  Is  a  swelling  of  the  subcutaneous  tissues  of  the  body  due 
to  an  abnormal  or  excessive  transudation  of  the  fluid  portion  of  the 
blood  into  or  its  abnormal  retention  in  the  lymph  spaces. 

Efferent.  (From  the  Latin  word  efferens,  "carrying  from.")  Carry- 
ing away,  as  the  efferent  nerves  conveying  impulses  away  from  the 
central  nerve  system;  also  bloodvessels  and  lymphatic  vessels  con- 
veying blood  and  lymph  respectively  from  the  tissues. 

Embryo.  (From  the  Greek  words  meaning  within,  to  swell  with). 
The  product  of  conception  up  to  the  fourth  month. 

Embryonic.    Pertaining  to  the  embryo. 

Emissive.    Sending  out,  as  nerve  impulses. 

Enarthrosis.  A  ball-and-socket  joint.  Like  the  articulation  of  the 
hip  and  femur. 

Encephalon.     (From  the  Greek  word  meaning  brain.)     Brain. 

Endo.     A  prefix  meaning  within. 


44d  GLOSSARY 

Endocardium.  (Within  the  heart.)  The  serous  membrane  lining 
the  interior  of  the  heart. 

Endolymph.    The  fluid  within  the  membranous  labyrinth  of  the  ear, 

Endomysium.  (Within  a  muscle.)  The  connective  tissue  between 
the  fibrils  of  a  muscle  bundle. 

Endoneurium.  (Within  a  nerve.)  The  delicate  connective  tissue 
holding  together  the  fibrils  of  a  bundle  of  nerves. 

Endosteum.  (Within  the  bone.)  The  vascular  membranous  layer 
of  connective  tissue  lining  the  medullary  cavity  of  long  bones. 

Endothelial  (cells).  Flat  cells  found  on  the  inner  surface  of  vessels 
and  spaces  that  do  not  communicate  with  the  external  air. 

Endothelium.  (From  the  Greek  words  meaning  within,  the  nipple.) 
See  Endothelial  (cell). 

Entoderm.  (From  the  Greek  words  meaning  within,  skin).  The 
inner  of  the  two  layers  of  cells  in  the  blastodermic  vesicles  of  the 
embryo. 

Enzyme.    Any  ferment  formed  within  the  living  organism. 

Ependymal.  Relating  to  the  ependyma — the  lining  membrane 
of  the  cerebral  ventricles  and  of  the  central  canal  of  the  spinal  cord. 

Epiblast.    Same  as  ectoderm.     (See  ectoderm.) 

Epicranial.  Relating  to  epicranium;  the  structures  covering  the 
cranium. 

Epidermis.  (From  the  Greek  words  meaning  upon,  the  skin.) 
The  outer  or  superficial  layer  of  the  skin. 

Epigastric.     Relating  to  the  epigastrium. 

Epigastrium.  (From  the  Greek  words  meaning  upon,  the  stomach.) 
The  upper  and  middle  part  of  the  abdominal  surface,  corresponding 
to  the  location  of  the  stomach. 

Epimysium.  (Upon  a  muscle.)  The  sheath  of  areolar  tissue  sur- 
rounding a  muscle. 

Epineurium.  (Upon  a  nerve.)  The  connective-tissue  sheath  of  a 
nerve  trunk. 

Epiphysis.  (From  the  Greek  words  meaning  upon,  to  grow.)  A 
process  of  bone  attached  for  a  time  to  another  bone  by  cartilage,  but 
soon  becoming  consolidated  with  the  principal  bone. 

Epitendinium.  (Upon  a  tendon.)  The  connective-tissue  sheath 
of  a  tendon. 

Epithelial.  (From  the  Greek  words  meaning  upon,  a  nipple.)  Per- 
taining to  epithelium. 

Epithelium.  (Upon  a  nipple.)  The  group  of  cells  that  forms  the 
epidermis  (outer  skin),  that  lines  all  membranes  of  canals  that  com- 
municate with  the  external  air,  and  that  are  specialized  for  secretion 
in  certain  glands,  as  the  liver,  kidney,  etc. 

Equilibrium.        (From    the    Latin    words    aequus    "equal;"    libra, 
"balance.")    A  state  of  balance. 
•  Erythrocyte.    A  red-blood  corpuscle  (a  small  body). 

Esophagus  or  (Esophagus.  (From  the  Greek  words  meaning  to 
carry,  to  eat.)  The  gullet.  The  musculomembranous  canal,  about 
9  inches  long,  extending  from  the  pharynx  to  the  cardiac  end  of  the 
stomach. 

Ethmoid  (bone).  (From  the  Greek  words  meaning  a  sieve,  likeness.) 
Sieve-like. 


GLOSSARY  441 

» 

Excretion.  (From  the  Latin  word  excernere,  "to  excrete.")  The 
discharge  of  waste  products  or  excretions  resulting  from  metabolism, 
by  the  skin,  kidneys,  etc. 

Extension.  (From  the  Latin  word  extendere,  "to  stretch  out.") 
A  straightening  out,  especially  the  muscular  movements  by  which 
a  limb  or  joint  is  extended. 

Extensors.  (A  group  of  muscles  which  straighten  or  extend  a  limb 
or  part  of  the  body. 

Extensor  Brevis  Digitorum.    The  short  extensor  of  the  toes  (digits). 

Extensor  Brevis  Pollicis.    The  short  extensor  of  the  thumb. 

Extensor  Carpi  Radialis  Longior  and  Brevier.  The  long  extensor  of 
the  radial  side  of  the  wrist  and  the  short  extensor  of  the  same  side. 

Extensor  Carpi  Ulnaris.    The  extensor  of  the  ulnar  side  of  the  wrist. 

Extensor  Communis  Digitorum.  The  common  extensor  of  the 
fingers  (digits). 

Extensor  Indicis  Proprius.    The  extensor  of  the  index  finger. 

Extensor  Longus  Digitorum.  The  long  extensor  of  the  fingers 
(digits). 

Extensor  Longus  Hallucis.    The  long  extensor  of  the  big  toe  (hallux). 

Extensor  Longus  Pollicis.    The  long  extensor  of  the  thumb. 

Extensor  Minimi  Digiti.     The  extensor  of  the  little  finger  (digit.) 

Extensor  Ossis  Metacarpi  Pollicis.  The  extensor  of  the  metacarpal 
bone  of  the  thumb. 

Extrinsic.  (From  the  Latin  word  extrinsicus,  "from  without.") 
External,  not  directly  belonging  to  a  part. 

Facet.  (From  the  French  word  facette,  "a  little  face.")  A  small 
plane  or  smooth  surface  on  a  bone,  usually  referring  to  the  articular 
facet. 

Falces  (pi.)  Cerebri  et  Cerebelli.  The  sickle-shaped  processes  of 
dura  mater  between  the  cerebrum  and  cerebellum,  respectively. 

Falciform.  (From  the  Latin  words  falx,  "a  sickle;"  forma,  "form.") 
Having  the  shape  of  a  sickle. 

Falx,  falcis  (Latin).    A  sickle. 

Fascia.  (From  the  Latin  word  fascia,  "a  band.")  The  areolar 
tissue  forming  the  layers  beneath  the  skin,  which  forms  sheaths  for 
muscles  and  vessels. 

Fascia  Lata.     (Broad  fascia.)    The  fascia  of  the  thigh. 

Fasciculus.  (Dim.  of  the  Latin  word  fascis,  a  bundle.")  A  little 
bundle;  as  of  muscle  fibers.    ^ 

Fauces.  (From  the  Latin  word  fauces,  "a  throat.")  The  space  at 
the  back  of  the  mouth  communicating  with  the  pharynx,  surrounded 
by  the  soft  palate  and  uvula  and  tonsils. 

Fauces  (isthmus  of).  The  opening  at  the  back  of  the  mouth  leading 
into  the  pharynx,  bounded  on  the  sides  by  the  arches  of  the  soft 
palate,  the  uvula  above,  the  base  of  the  tongue  below. 

Fecundation.  (From  the  Latin  word  fecundus,  "fruitful.")  The 
act  of  making  fruitful;  impregnation;  as  the  spermatozoon  (male) 
fecundates  the  ovum  (female). 

Femoral.    Pertaining  to  the  femur,  as  arteries,  veins,  and  muscles. 

Femur.     (From  the  Latin  word  femur,  "thigh  bone.") 

Fenestra  Ovalis.  (From  the  I^atin  words  fenestra,  "a  window;" 
ovalis,    "egg-shaped,"    from   ovum,    "an   egg.")      The   oval   window 


442  GLOSSARY 

located  in  the  vestibule  of  the  internal  ear;  which  communicates  with 
the  middle  ear  or  tympanum  closed  in  life  by  the  stapes,  an  ossicle 
of  the  ear.    (See  Ossicle.) 

Ferment.  (From  the  Latin  word  fermentum,  "leaven,  yeast.") 
Any  substance  which  in  contact  with  another  substance  is  capable 
of  setting  up  changes — called  fermentation — in  the  latter,  without 
itself  undergoing  much  change.  Ferments  are  classified  into  unorgan- 
ized or  soluble,  and  organized,  or  living  ferments. 

Fermentation.  The  decomposition  of  complex  molecules  of  chemical 
bodies  or  substances  under  the  influence  of  ferments — called  enzymes. 

Fetus.  (From  the  Latin  word  fetus,  "offspring").  The  unborn  off- 
spring of  vivaparous  (producing  young  in  a  living  state)  animals  in  the 
later  stage  of  development. 

FibrocartiUge.     Cartilage  with  fibrous  tissue  intermixed. 

Fibrous  (From  the  Latin  word  fibra,  "a  fiber.")  Containing  fibers; 
of  the  character  of  fibrous  tissue. 

Fibula.    (Latin,  "a  buckle.")    The  bone  on  the  outer  side  of  the  leg. 

Fibular.    Pertaining  to  the  fibula. 

Filium  Terminate.  A  long,  slender  thread  of  nerve  fibers  enclosed 
by  the  dura  mater,  practically  the  termination  of  the  spinal  cord. 

Fimbriae  (pi.  of  fimbria).  (From  the  Latin  word  fimbria,  "a  fringe"). 
A  fringe.  The  fimbriae  of  the  Fallopian  tube;  the  fringe-like  processes 
of  the  outer  extremity  of  the  tube. 

Fimbriated .    Fringed . 

Flexion.  (From  the  Latin  word  flecture,  "to  bend.")  The  act  of 
bending,  especially  the  muscular  movements  by  which  a  limb  or 
joint  is  bent. 

Flexors.  A  group  of  muscles  which  bend  a  limb  or  part  of  the 
body.    The  opposite  of  the  extensors. 

Flexor  Brevis  Digitorum.    The  short  flexor  of  the  toes. 

Flexor  Brevis  Hallucis.    The  short  flexor  of  the  big  toe. 

Flexor  Brevis  Minimi  Digiti.    The  flexor  of  the  little  finger  and  toe. 

Flexor  Brevis  Pollicis.    The  short  flexor  of  the  thumb. 

Flexor  Carpi  Radialis.    The  flexor  of  the  radial  side  of  the  wrist. 

Flexor  Carpi  Ulnaris.    The  flexor  of  the  ulnar  side  of  the  wrist. 

Flexor  Longus  Digitorum.    The  long  flexor  of  the  toes. 

Flexor  Longus  Hallucis.    The  long  flexor  of  the  big  toe.  (See  Hallux.) 

Flexor  Longus  Pollicis.    The  long  flexor  of  the  thumb.    (See  Polhcis.) 

Flexor  Profundus  Digitorum.    The  deep  flexor  of  the  fingers. 

Flexor  Sublimis  Digitorum.    The  superficial  flexor  of  the  fingers. 

Follicle.  (From  the  Latin  word  folliculus,  a  dim.  of  follis,  "bellows.") 
Arranged  in  the  form  of  a  little  sac,  as  the  lymph,  hair  follicles,  etc. 

Fontanelle.  (From  the  Latin  word  fontanella,  "a  little  fountain.") 
A  membranous  space  between  the  angles*ibf  junction  of  the  sutures 
of  the  cranial  bones  in  fetal  life  and  infan^. 

Foramen  Magnum.    The  great  opening.    In  occipital  bone. 

Foramen  Ovalis.  The  oval  opening.  In  the  waU  between  the 
auricles  of  the  heart  in  the  fetus,  and  for  ten  days  to  two  weeks  it 
persists  in  infant  hearts. 

Foramen  Rotundum.     The  round  opening.    In  sphenoid  bone. 

Foramina  or  Foramen.  (From  the  Latin  word  forare,  to  pierce.) 
An  opening  or  perforation,  especially  a  bone. 


GLOSSARY  443 

Fossa  (pi.  ae).    (Latin,  fossa,  "a  ditch.")    A  depression  or  ditch. 

Fossa  Ovalis.    The  oval  ditch. 

Fovea.    (From  the  Latin,  "a  small  ditch.")    A  small  depression. 
--  Funiculus.     (Dim.  of  the  Latin  word  funis,  "a  rope  or  cord.")      A 
cord-like  structure. 

Fuse.     (From  the  Latin  word  fundere,  "to  pour  out."«)  To  unite  with. 

Fusiform.  (From  the  Latin  words  fusus,  "a  spindle;"  forma, 
"shape.")    Spindle-shape. 

Galactophorous.    Milk-bearing. 

Ganglion  or  Ganglia.  (From  the  Greek  word  meaning  a  knot.)  A 
well-defined  group  of  nerve  cells  and  fibers  forming  an  underlying 
nerve  centre. 

Gastric.  (From  the  Greek  word  meaning  stomach.)  Pertaining  to 
the  stomach. 

Gastrocnemius.  A  double-head  muscle  forming  with  the  soleus 
the  calf  of  the  leg. 

Genitals  (Genitalia).  (From  the  Latin  word  genitalis,  "pertaining 
to  generation,"  from  gignere,  "to  beget.")  Relating  to  the  organs  of 
generation  or  reproduction  in  the  male  or  female. 

Genito-urinary.    Relating  to  the  genitalia  and  urinary  organs. 

Germinal.  (From  the  Latin  word  germen,  "a  germ.")  Pertaining 
to  the  development  of  a  tissue  or  organ. 

Gestation.     (From  the  Latin  word  gestare,  "to  bear.")    Pregnancy, 

Glenoid.    Resembling  a  shallow  cavity. 

Glia  (cells).  (From  the  Greek  word  meaning  glue.)  The  cells 
found  in  the  neuroglia  (the  tissue  which  forms  the  basis  of  the  sup- 
porting frame- work  of  the  nerve  tissue  of  the  cerebrospinal  system) . 

Globule.  (From  the  dim.  of  the  Latin  word  globus,  "a  ball.") 
A  small  spheric  body,  as  fat  globules,  etc. 

Glomerulus.  (From  the  Latin  word  glomerulus,  ''a  little  ball.")  A 
small,  rounded  mass,  as  the  coil  of  bloodvessels  projecting  into  the 
expanded  end  of  each  uriniferous  tubule  and  with  it  forming  the 
Malpighian  body  or  corpuscle. 

Glottis,  idis  (Rima).    The  space  between  the  vocal  cords. 

Gluteus.  (From  the  Greek  word  meaning  buttock.)  Referring  to 
muscles  of  the  buttock. 

Gluteus  Maximus.  The  greatest  of  the  buttock.  (Literal  trans- 
lation.) 

Gluteus  Medius.    The  medium-sized  of  the  buttock. 

Gluteus  Minimus.    The  smallest  of  the  buttock 

Glycogen.  A  carbohj^drate  found  in  the  liver  cells.  It  is  stored 
in  the  liver,  where  it  is  converted,  as  the  system  requires,  into  sugar 
(glucose) . 

Gramme  (gm.) .  The  unit  of  the  measurement  by  weight  of  the  metric 
system  of  weights  and  measures.     1  gm,  =  15.432  grains. 

Granular.  (From  the  Latin  word  granula,  "a  little  grain.")  Per- 
taining to  granule.    As  the  granular  appearance  of  a  cell. 

Granule.  (From  the  Latin  word  granula,  "a  small  grain.")  A 
small  body  or  grain,  as  the  granules  of  a  cell. 

Gustatory  (nerve).  (From  the  Latin  word  gustare,  "to  taste.") 
Pertaining  to  the  sense  of  taste,  as  the  gustatory  nerve — the  nerve 
of  taste  in  the  tongue. 


444  GLOSSARY 

Gyrus  (pi.  gyri  or  gyre).    A  convolution  of  the  brain. 

Hallux,  Hallucis.    From  the  Latin.    The  great  toe. 

Hemoglobin.    The  coloring  matter  of  the  red  cells  of  the  blood. 

Hepar.    From  the  Greek  word  meaning  liver. 

Hepatic.  Pertaining  to  the  liver,  as  hepatic  artery,  hepatic  duct, 
and  hepatic  vein. 

Hiatus  (Fallopii).  (From  the  Latin  word  hiare,  "to  gape.")  A 
space  or  opening.  Hiatus  Fallopii:  A  shallow  grove  on  the  petrous 
portion  of  the  temporal  bone  for  the  passage  of  a  nerve,  etc. 

Hilum.  A  pit,  recess,  or  opening  in  an  organ,  usually  for  the  entrance 
and  exit  of  vessels  or  ducts,  as  the  hilum  of  the  kidney,  spleen,  etc. 

Histology.    The  minute  or  microscopic  anatomy  of  the  tissues. 

Homogeneous.  Having  a  uniform  appearance  or  character  in  all 
its  parts  or  substance. 

Humerus  (bone).  (From  the  Latin,  "arm.")  The  long  bone  of 
the  arm  extending  from  the  shoulder  to  the  elbow. 

Hyaline.    Resembling  glass. 

Hymen.  The  portion  of  mucous  membrane  which  partially  occludes 
the  opening  of  the  vagina. 

Hyoid  (bone).  (Having  the  form  of  the  Greek  letter  upsilon  T.)  A 
bone  situated  between  the  root  of  the  tongue  and  the  larynx,  supporting 
the  tongue  and  giving  attachment  to  some  of  the  muscles  of  the  tongue, 
pharynx,  and  floor  of  the  mouth. 

Hyperemic.    Pertaining  to  the  excessive  blood  in  a  part  (hyperemia). 

Hypochondriac.    Pertaining  to  the  hypochondrium. 

Hypochondrium.  The  upper  lateral  surface  of  the  abdomen  and 
thorax  corresponding  to  the  lower  ribs. 

Hypogastrium.  The  lower  anterior  surface  of  the  abdomen  above 
the  pubes. 

H3rpothenar.  The  fleshy  eminence  on  the  palm  of  the  hand  over 
the  metacarpal  bone  of  the  little  finger. 

Heum.  (From  the  Greek  word  meaning  to  roll.)  The  lower  portion 
of  the  small  intestine  ending  in  the  cecum. 

Hiopectineal.  (From  the  Latin  words  ihum,  "flank;"  pectens, 
"comb.")  The  line  pertaining  conjointly  to  the  ilium  and  os  pubis 
(bones) . 

Iliotibial  (band).  (From  the  Latin  words  ilium,  "flank;"  tibia, 
"tibia.")  The  thickened  portion  of  the  fascia  lata  of  the  thigh  which 
extends  from  the  ilium  to  the  tibia. 

nium  (bone).  Latin,  "the  flank.")  The  superior  expanded  portion 
of  the  innominate  bone. 

Impregnation.  (From  the  Latin  word  impregnare,  "to  impreg- 
nate.")   The  act  of  rendering  pregnant;  fecundation. 

Inferior  Obliquus  Oculi  (muscle).  The  inferior  oblique  of  the 
eye-ball. 

Infundibulum.  (From  the  Latin  word  infundere,  "to  pour  into.") 
A  funnel-shaped  passage  or  part. 

Inguinal.     (From  inguen,  "the  groin.")    Pertaining  to  the  groin. 

Inhibitor  (nerve).  (From  the  Latin  inhibere,  "to  check.")  To 
check  or  hold  back.  Inhibitor  nerve:  One  which  has  a  controlling 
influence  upon  a  nerve  conveying  impulses  to  certain  organs  and 
tissues  of  the  body. 


GLOSSARY  445 

Innominate.  (From  the  Latin  words  in,  "without;"  nomen,  "a 
name.")  Unnamed,  unnamable;  as  innominate  bone  or  artery,  due  to 
its  not  resembUng  any  known  object. 

Inorganic.  Not  organic;  not  produced  by  animal  or  vegetable  organ- 
isms, as  an  inorganic  compound. 

Insalivation.  (From  the  Latin  words  in,  "in;"  saliva,  "the  spittle.") 
The  act  of  mixing  the  food  with  saliva  when  chewed  (mastication) . 

Inter.  (From  the  Latin  word  inter,  "between.")  Between  any 
structures. 

Interarticular.    Between  joints. 

Interauricular.    Between  the  auricles  of  the  heart. 

Intercellular.    Between  the  cells. 

Intercondylar.  Between  the  condyles,  as  the  intercondylar  notch  of 
the  femur  bone. 

Intercostal.  Between  the  ribs,  as  intercostal  muscles,  arteries,  nerves, 
and  spaces. 

Interlobular.  Between  the  lobules  of  the  liver,  referring  to  inter- 
lobular veins  and  arteries. 

Intermuscular  (septa).    Between  muscles. 

Interosseous.    Between  bones. 

Intertrochanteric  (line).    Between  the  trochanters  of  femur. 

Interventricular.    Between  the  ventricles  of  the  heart. 

Intralobular.  (From  the  Latin  words  intra,  "within;"  lobulus,  "a 
little  lobe.")    Within  a  lobule,  as  an  intralobular  vein  of  liver. 

Intrinsic.  (From  the  Latin  word  intrinsecus,  "on  the  inside.") 
Inherent,  situated  within;  peculiar  to  a  part,  as  the  intrinsic  muscles 
of  the  eye. 

Involuntary.  (From  the  Latin  words  in,  "not;"  velle,  "to  will.") 
Performed  or  acting  independently  of  the  will,  as  involuntary  muscle. 

Ischium.  The  bone  forming  the  back  and  lower  part  of  the  innomi- 
nate bone. 

Jejunum.  (From  the  Latin  word  jejenus,  "empty;"  because  it  is 
usually  found  empty  after  death.)  The  second  portion  of  the  small 
intestine  extending  between  the  duodenum  and  ileum  and  measuring 
about  eight  feet  in  length. 

Katabolism.  Physiologic  disintegration  of  the  products  of  metab- 
olism.   The  opposite  of  anabolism.     (See  Anabolism.) 

Kinetic  (energy).  (From  the  Greek  word  meaning  to  move.) 
Producing  motion. 

Labyrinth.  (From  the  Greek  word  meaning  a  maze.)  The  name 
given  to  the  series  of  cavities  of  the  internal  ear  comprising  the  vesti- 
bule, cochlea,  and  semicircular  canals. 

Lacrimal.  (From  the  Latin  word  lacrima,  "a  tear.")  Pertaining 
to  the  tears,  or  the  organs  containing  or  secreting  them. 

Lactation.  (From  the  Latin  word  lactere,  "to  suckle.")  The 
period  during  which  the  child  is  nourished  from  the  breast. 

Lacteal.  (From  the  Latin  word  lac,  "milk.")  Resembhng  milk. 
Any  one  of  the  lymphatic  ducts  of  the  villi  of  the  small  intestine  which 
take  up  the  chyle;  the  chyle  resembling  milk  as  to  color. 

Lacuna  (pi.  se).  (From  the  Latin  word  lacus,  "a  lake.")  A  lake, 
as  the  lacunae  of  bone  construction. 

Lamella  (pi.  ae).  (Dim.  of  the  Latin  word  lamina,  "a  plate.")  A 
thin  scale  or  plate. 


446  GLOSSARY 

Lamina  (pi.  se).    Latin.    A  plate. 

Lamina  Spiralis.    A  spiral  plate. 

Larjmx.  The  organ  of  voice  situated  between  the  base  of  the  tongue 
and  the  trachea. 

Lateral.  (From  the  Latin  word  latus,  ''the  side.")  At,  belonging 
to,  or  pertaining  to  the  side.  Situated  on  either  side  of  the  middle 
vertical  plane. 

Latissimus  Dorsi  (muscle).    The  widest  of  the  back. 

Levator  Anguli  Oris.    The  elevator  of  the  angle  of  the  mouth. 

Levator  Labii  Superioris  Alseque  Nasi.  The  elevator  of  the  upper 
lip  and  the  wing  of  the  nose. 

Levator  Menti.    The  elevator  of  the  chin. 

Levator  Palati.    The  elevator  of  the  palate. 

Levator  Palpebrse  Superioris.    The  elevator  of  the  upper  eyelid. 

Leukocyte.  A  white-blood  cell  or  corpuscle,  seen  in  the  blood; 
microscopic. 

Ligamentum  Patellae.     The  ligament  of  the  patella  (knee-cap  bone) . 

Linea  Alba.    White  line. 

Linea  Aspera.    Rough  line  on  the  posterior  aspect  of  the  femur. 

Linea  Semilunaris.  (From  the  Latin  words  linea,  "a  line;"  semi- 
lunaris, from  semi,  "half;"  luna,  "a  moon.")  The  line  resembling 
a  half  moon  in  shape. 

Linea  Transversa.    The  transverse  line. 

Liter.  (From  the  Latin  word  litra,  "a  pound.")  The  unit  of  capa- 
city in  the  metric  system.    One  liter  equals  1.76  pints. 

Lobule.  (From  the  Latin  word  lobulus,  dim.  of  lobus,  "a  lobe.") 
A  small  lobe. 

Locomotion.  (From  the  Latin  words  locus,  "a  place;"  motio, 
"motion,"  from  movere,  "to  move.")  The  act  of  moving  from  place 
to  place,  as  in  walking,  etc. 

Lumbar.  (From  the  Latin  word  lumbus,  "a  loin.")  Pertaining 
to  the  loins  or  lower  part  of  back. 

Lymphocyte.  A  lymph  cell.  Belonging  to  the  group  of  white  cells. 
Seen  in  the  blood;  microscopic. 

Lymphoid.     Having  the  appearance  or  character  of  lymph. 

Major  Calices.    The  larger  calices  (see  Calices). 

Malar.  (From  the  Latin  word  mala,  "cheek.")  Pertaining  to  the 
cheek  bone.    The  bone  of  the  prominence  of  the  cheek. 

Malleolus.  (Dim.  of  the  Latin  word  malleus,  "a  hammer.")  A  part 
or  process  of  bone  having  a  hammer-head  shape.  As  the  malleolus 
of  the  tibia  and  fibula. 

Mandible.  (From  the  Latin  word  mandere,  "to  chew.")  The  jaw 
bone. 

Mastication.  (Frgm  the  Latin  word  masticare,  "to  chew.")  The 
act  of  chewing. 

Mastoid.  (Resembling  the  shape  of  a  nipple.)  Pertaining  to  the 
mastoid  process. 

Maxilla  (jaw  bone).    The  bone  of  the  upper  or  lower  jaw. 

Maximus.    The  greatest. 

Meatus.  (From  the  Latin  word,  meare,  "to  flow  or  pass.")  An 
opening  or  passage.    Auditory  meatus,  etc. 

Medius.    The  middle. 


GLOSSARY  447 

Medulla.  The  marrow.  Anything  resembling  marrow,  as  the 
medulla  oblongata.    Also  the  central  part  of  an  organ. 

Medullated.  Containing  or  covered  by  a  substance  resembling 
medulla  or  marrow.    Medullated  nerves  covered  with  a  myelin  sheath. 

Mediastinuxxi.  (From  the' Latin  words  in,  medio,  stare,  "to  stand 
in  the  middle.")  The  space  in  the  middle  of  the  chest  between  the 
two  pleurae,  divided  into  anterior,  middle,  posterior,  and  superior 
mediastinum. 

Membrane.  (From  the  Latin  word  membrana,  from  membrum, 
"a  member.")  A  thin  layer  of  tissue  lining  or  surrounding  a  part  or 
separating  adjacent  cavities. 

Mesentery.  A  fold  of  peritoneum  which  connects  the  intestine 
with  the  posterior  abdominal  wall. 

Meshes.    Net-work,  reticular. 

Mesocolon.  The  fold  of  peritoneum  connecting  the  colon  with  the 
posterior  abdominal  wall. 

Mesoderm.  The  middle  layer  of  the  blastodermic  vesicle  of  the 
embryo,  derived  from  both  the  ecto-  and  entoderm. 

Mesogastrium  or  Umbilical.  The  region  corresponding  to  the 
part  of  the  abdominal  wall  surrounding  the  umbilicus  (navel). 

Metabolism.  The  group  of  phenomena  occurring  in  the  tissues 
whereby  the  organic  beings  transform  foodstuffs  into  complex  tissue 
elements  (anabolism),  and  convert  complex  substances  into  simple 
ones  in  the  production  of  energy  (katabolism) . 

Metacarpal.    Relating  to  the  metacarpus. 

Metacarpus.  (From  the  Greek  words  meaning  beyond  the  wrist.) 
That  part  of  the  hand  between  the  bones  of  the  wrist  and  the  bones 
of  the  fingers. 

Metatarsal.    Pertaining  to  the  metatarsus. 

Metatarsus.  (From  the  Greek  words  meaning  beyond  the  instep.) 
That  part  of  the  foot  between  the  bones  of  the  instep  and  the  bones 
of  the  toes. 

Micturition.  (From  the  Latin  word  micturire,  "to  pass  water.") 
The  act  of  passing  urine. 

Millimeter  (mm.).  The  thousandth  part  of  a  meter.  Equal  to 
0.039370  inch. 

Minimus.    The  least,  smallest. 

Minor.    The  lesser,  smaller. 

Minor  Calices.    The  smaller  calices. 

Mitral  (bicuspid).  (Resembling  a  miter,  a  covering  for  the  head 
worn  by  popes,  bishops,  and  cardinals.)  The  valves  of  the  left  auriculo- 
ventricular  opening  of  the  heart. 

Molecular.  (From  the  Latin  word  mole,  "a  mass").  Pertaining 
to  or  composed  of  molecules. 

Molecule.  (From  the  Latin  word,  a  dim.  of  moles,  "mass.")  The 
minute  portion  of  matter.  In  physics  the  smallest  quantity  into  which 
a  substance  can  be  divided  and  retain  its  characteristic  properties; 
or  the  smallest  quantity  of  any  gas,  liquid,  or  solid  that  can  exist  in 
a  free  state. 

Motor.  (From  the  Latin  word  movere,  "to  move.")  Moving  or 
causing  motion.  Concerned  or  pertaining  to  motion,  as  motor  cells, 
motor  nerves,  motor  centre. 


448  GLOSSARY 

Mucous.    Containing  or  having  the  nature  of  mucous. 

Multipolar.  (From  the  Latin  words  multus,  many;  polus,  "a  pole.") 
Having  many  poles,  as  multipolar  nerve  cells,  having  many  processes. 

Myelinic.  Relating  to  myelinic  nerve  fibers,  those  possessing  a 
myelin  sheath. 

Myocardium.    The  muscular  tissue  of  the  heart. 

Myosin.  (From  the  Greek  word  meaning  muscle.)  A  protein 
of  the  globuhn  class,  found  in  coagulated  muscle-plasma,  and  formed 
from  the  antecedent  globulin  myosinogen.         "* 

Naris  (pi.  es).  (From  the  Latin  word  n-aris,  "the  nostril.")  One 
of  a  pair  of  openings  at  the  anterior  or  posterior  part  respectively  of 
the  nose. 

Nasal.  (From  the  Latin  word  nasus,  "the  nose.")  Pertaining  to 
the  nose. 

Nervus  Intermedins.  The  nerve  situated  between,  as  the  Nervus 
intermedius  between  the  facial  and  auditory  nerves. 

Neural  (canal).  Pertaining  to  nerves.  Neural  canal:  The  bony 
canal  comprising  the  cavity  of  the  cranium  and  vertebral  column 
which  contains  the  central  nerve  system. 

Neurilemma.    The  sheath  encasing  a  nerve  fiber. 
^  Neuroglia.     The  tissue  forming  the  basis  of  the  supporting  frame- 
work of  the  nerve  tissue.    It  consists  of  gha  cells. 

Neurone  or  Nerve  Cell.  One  of  the  countless  number  of  units  of 
which  the  nerve  system  is  composed.  The  basis  for  all  nerve  tissue 
activity. 

Node.  (From  the  Latin  word  nodus,  "a  swelling.")  A  knob, 
swelling,  or  protuberance. 

Nodvde.  (Nodulus,  dim.  of  nodus,  "a  swelling.")  A  small  node  or 
swelling. 

Nucha  (pi.  ae).  (Ligamentum  nuchae.)  (From  the  Latin  word  nucha, 
"nape  of  neck.")    The  ligament  of  the  nape  of  the  neck. 

Nucleated.    Possessing  a  nucleus. 

Nucleolus.  (Dim.  of  nucleus  from  nux,  "  a  nut.")  The  small  rounded 
body  within  the  cell  nucleus. 

Nucleus.  (From  the  Latin  word  nux,  "a  nut.")  The  essential  part 
of  a  typical  cell,  usually  round  in  outhne,  and  situated  near  the  centre. 

Nutrient  Canal.  One  that  affords  nourishment,  as  the  nutrient 
canal  of  a  bone,  which  contains  a  nutrient  artery. 

Obturator.  (From  the  Latin  word  obturare,  "to  stop  up.")  That 
which  closes  an  opening;  as  obturator  membrane  or  foramen  of  innomi- 
nate bone. 

Occipital  (bone).    Pertaining  to  the  occiput.     (See  Occiput.) 

Occipitofrontalis  (muscle).    From  the  occiput  to  the  forehead. 

Occiput.  (From  the  Latin  words  ob,  "against;"  caput,  "the  head.") 
The  back  part  of  the  head. 

Odontoid.     Resembling  a  tooth. 

Olecranon  (process) .  The  large  convex  portion  of  the  back  part  of 
the  upper  end  of  the  ulna.  The  point  of  the  elbow  felt  beneath  the 
skin. 

Olfactory.  (From  the  Latin  word  olfacere,  "to  smell.")  Pertaining 
to  the  sense  of  smell. 


GLOSSARY  449 

Omentum.  Any  fold  of  peritoneum  attaching  an  organ  to  the 
stomach.  The  greater  omentum  overhes  the  small  intestines  like 
an  apron. 

Opponens.  (From  the  Latin  words  ob,  "against;"  ponere,  "to 
place.")    Opposing. 

Opponens  Minimi  Digit!  (muscle).  The  muscle  which  places  the 
little  finger  opposite  to  the  thumb. 

Opponens  Pollicis  (muscle).  The  muscle  which  places  the  thumb 
opposite  to  the  little  finger. 

Optic  Chiasm.    (See  Chiasm.) 

Orbicularis  Oris  (muscle).  From  the  Latin  word  orbiculus,  a  dim. 
of  orbis,  "a  circle.")     The  circular  one  of  the  mouth. 

Orbicularis  Palpebrarum  (muscle).    The  circular  one  of  the  eyelids. 

Orbit.  (From  the  Latin  word  orbita,  from  orbis,  "a  circle.")  The 
bony  pyramidal  cavity  containing  the  eye  and  its  muscles,  etc. 

Orbital.    Pertaining  to  the  orbit. 

Organic.  (From  the  Greek  word  meaning  an  organ.)  Having  or 
pertaining  to,  or  characterized  by  organs;  relating  to  the  animal  and 
vegetable  worlds;  affecting  the  structure  of  organs. 

Orifice.  (From  the  Latin  words  orificium;  os,  "a  mouth;"  facere, 
"to  make.")  An  opening  or  outlet  of  hollow  organs,  or  between 
organs. 

Os  Innominata  (bone)  (pi.  ossa  innominatse).  (From  the  Latin 
OS,  "a  bone;"  innominata,  in,  "without;"  nomen,  "a  name.")  The 
nameless  bone,  due  to  its  not  resembling  any  known  object. 

Os  Magnum.  (The  great  bone.)  The  third  bone  of  the  second 
row  of  carpal  bones  (bones  of  the  wrist). 

Osmosis.  (The  passage  of  liquids  and  substances  in  solution  through 
porous  septa  (a  partition). 

Osseocartilaginous.  Formed  of,  or  pertaining  to  bone  and  cartilage 
as  one. 

Ossicle.  (From  the  Latin  word  ossiculum,  a  dim.  of  os,  "a  bone.") 
A  small  bone.  Auditory  ossicles  or  chain  of  small  bones  found  in  the 
middle  ear.    They  are  the  incus,  stapes,  and  malleus. 

Ossification.  From  the  Latin  words  os,  "  a  bone;"  facere,  "to  make.") 
The  process  of  bone  formation. 

Osteoblasts.  Cells  concerned  in  the  formation  of  bony  tissue 
durinp;  osriifi^"^'''^^^ 

Osteoclasts.  The  multinuclear  (many  nuclei)  cells  found  against 
the  surface  of  bone  in  little  eroded  depressions  (Howship's  fovea), 
and  concerned  in  the  removal  of  bone. 

Ostium  Uterinum  or  Uteri.    The  mouth  of  the  uterus  (womb) . 

Ovum.  (From  the  Latin  word  ovum,  "an  egg.")  The  reproductive 
cell  of  an  animal  or  vegetable,  an  egg. 

Oxidation.  (From  the  Greek  word  meaning  sharp.)  The  act  or 
process  of  combining  with  oxygen,  as  the  hemoglobin  of  the  red  cells 
does  during  respiration,  and  the  cells  of  the  tissues  combine  with  it 
as  the  hemoglobin  of  the  red  cells  in  the  blood  gives  it  up  upon  reaching 
them.    Oxidation  is  essential  to  body  metabolism. 

Oxygen.  Is  a  colorless,  tasteless,  odorless  gas,  one  of  the  non- 
metallic  elements.  It  constitutes  one-fifth  of  the  atmosphere,  eight- 
ninths  of  water,  three-fourths  of  organized  bodies,  and  about  one-half 
29 


450  GLOSSARY 

the  crust  of  the  globe.  It  is  essential  to  combustion  or  burning  with 
the  elimination  of  heat  and  light  when  oxidation  takes  place.  It  is  not 
a  food,  but  is  essential  to  the  act  of  respiration.  Its  absence  causes 
asphyxia  or  suffocation. 

Palate.    The  roof  of  the  mouth. 

Palmaris  Brevis  (muscle).    The  short  one  of  the  palm. 

Palmaris  Longus  (muscle).    The  long  one  of  the  palm. 

Palpebral.    Pertaining  to  the  eyelid. 

Papilla  (pi.  se).  (From  the  Latin  papilla,  "a  nipple.")  A  small 
nipple-like  eminence. 

Parietal.  (From  the  Latin  word  paries,  "a  wall.")  Forming  or 
pertaining  to  the  wall  of  a  cavity,  or  portion  of  a  membrane  attached  to 
it,  as  parietal  peritoneum,  etc. 

Pars  Intermedius.  The  part  between,  referring  to  the  nervus 
intermedins.)     (See  N.  intermedius.) 

Parturition.  (From  the  Latin  word  parturitio,  from  partuire,  "to 
bring  forth.")    The  act  of  giving  birth  to  the  young. 

Patella  (bone).  (From  the  Latin  word  a  dim.  of  patera,  "a  shallow 
dish.")  The  knee-pan,  or  knee-cap;  a  round  small  bone  in  front  of 
the  knee,  developed  in  the  tendon  of  the  quadriceps  extensor  muscle. 

Pectoral.  (From  the  Latin  word  pectus,  "a  breast.")  Pertaining 
to  the  chest. 

Pectoralis  Major  (muscle).    The  larger  one  of  the  chest. 

Pectoralis  Minor  (muscle).    The  smaller  one  of  the  chest. 

Pedicle.  (From  the  Latin  word  pediculus,  dim.  of  pes,  pedis,  "a 
foot.")    A  slender  process  acting  as  a  foot  or  stem. 

Peduncle.  (From  pedunculus,  a  dim.  of  pes,  "a  foot.")  A  narrow 
part  acting  as  a  support. 

Pelvic.    Pertaining  to  the  pelvis. 

Pelvis.  (From  the  Latin  word  pelvis,  "a  basin.")  A  basin-shaped 
cavity.  The  bony  ring  formed  by  the  two  innominate  bones  and  the 
sacrum  and  coccyx. 

Peptone.  The  final  protein  body  or  substance  formed  by  the  action 
of  ferments  on  albumins  during  gastric  and  pancreatic  digestion. 

Peri.    A  Greek  prefix  signifying  around. 

Pericardium.  (Around  the  heart.)  The  serous  membrane  sur- 
rounding the  heart. 

Perichondrium.  The  fibrous  connective  tissue  surrounding  the 
surface  of  cartilage. 

Perimysium.  (Around  a  muscle.)  The  connective  tissue  surrounding 
the  primary  bundles  of  muscle  fibers. 

Perineum.  That  portion  of  the  body  corresponding  to  the  struc- 
tures overlying  the  outlet  of  the  pelvis. 

Periosteum.  (Around  bone.)  A  fibrous  membrane  investing  the 
surface  of  bones. 

Peripheral.    Pertaining  to  or  placed  near  the  periphery. 

Periphery.  (From  the  Greek  words  meaning  around,  to  carry.) 
The  circurnference;  the  external  surface,  or  extreme  portions  of  the 
body  or  an  organ. 

Peristalsis.  A  peculiar  wave-like  movement  seen  in  tubes  provided 
with  longitudinal,  transverse,  and  oblique  muscle  fibers,  as  the  intes- 
tinal canal,  stomach,  etc. 


GLOSSARY  451 

Peristaltic.    Pertaining  to  peristalsis. 

Peritendineum.  (Around  a  tendon.)  The  fibrous  sheath  investing 
the  small  bundles  of  tendon  fibers. 

Peritoneum.  (From  the  Greek  words  meaning  around,  to  stretch.) 
The  serous  membrane  lining  the  interior  of  the  abdominal  cavity  and 
surrounding  the  contained  viscera.  It  forms  folds  for  the  support  of 
organs  called  ligaments  (of  liver,  uterus,  etc.);  attaches  organs  to 
each  other,  as  omentum  when  another  organ  is  connected  to  the 
stomach,  thus  gastrosplenic  omentum;  as  the  intestines  are  held  to 
the  posterior  abdominal  wall:  thus  the  mesentery;  as  the  colon  is 
attached  to  the  wall  of  the  abdomen :  thus  the  mesocolon.  The  organs 
behind  the  peritoneum  are  spoken  of  as  retroperitoneal  organs. 

Peroneal.  Pertaining  to  the  fibula  bone.  The  region  overlying  the 
fibula. 

Peroneus  Brevis  (muscle).     The  short  peroneal. 

Pferoneus  Longus  (muscle).     The  long  peroneal. 

Pes  Anserinus.  (From  the  Latin  word  pes,  "a,  foot;"  anserinus,  "a 
goose")-  A  goose  foot;  named,  as  the  branches  of  the  facial  nerve  are 
supposed  to  spread  hke  the  toes  of  a  goose  foot. 

Petrous.  (From  Greek  word  meaning  rock,  stony,  of  the  hardness 
of  stone.) 

Phalanx  (pi.  phalanges).     One  of  the  bones  of  the  fingers  or  toes. 

Pharynx.  (From  the  Greek  word  meaning  throat).  The  musculo- 
membranous  tube  situated  back  of  the  nose,  mouth,  and  larynx. 

Phrenic.  Pertaining  to  the  diaphragm  or  diaphragmatic  region, 
surface,  etc. 

Pia  Mater.  (From  the  Latin  words  pia,  "tender;"  mater,  "mother.") 
The  tender  mother.  The  vascular  membrane  enveloping  the  surface 
of  the  brain  and  spinal  cord. 

Pigment.  (From  the  Latin  word  pingere,  "to  paint.")  A  coloring 
matter,  or  dye-stuff.  Pigments  may  be  in  solution  or  in  the  form  of 
granules  or  crystals;  as  the  pigment  of  skin  in  negroes,  etc.;  iris  of  eye. 

Pisiform  (bone).  (From  the  Latin  words  pisum,  "a  pea;"  forma, 
"form.")    Pea-shaped.    A  bone  of  the  wrist. 

Placenta.  (From  the  Greek  word  meaning  a  cake.)  The  organ  on 
the  wall  of  the  uterus  to  which  the  embryo  is  attached  by  means  of 
the  umbilical  cord  and  from  which  it  receives  its  nourishment  and 
excretes  the  waste  products  from  about  the  third  month  of  gestation 
to  the  birth  of  the  child  (parturition).  It  is  called  the  "after-birth" 
by  the  laity. 

Placental.    Referring  to  the  placenta. 

Plantar.  (From  the  Latin  word  planta,  "the  sole  of  the  foot.") 
Referring  to  the  sole  of  the  foot. 

Plasma.    The  fluid  part  of  the  blood  and  lymph. 

Platysma  Myoides  (muscle)..  The  broad  muscle  (from  the  Greek). 

Pleura.  (From  the  Greek  word  lyieaning  a  rib.)  The  serous  meni- 
brane  covering  the  lungs  and  inner  surface  of  the  wall  of  the  thoracic 
cavity. 

Pollicis.  (From  the  Latin  word  pollen,  poUicis,  "the  thumb.") 
Of  the  thumb. 

Polygonal.    Having  many  angles. 

Polyhedral.    Having  many  sides. 


452  GLOSSARY 

Potential  (energy).  (FromtheLatin  word  potens,  "able.")  Capable 
of  acting  or  doing  work. 

Poupart's  Ligament.  The  ligament  extending  from  the  anterior 
superior  spine  of  the  iliac  bone  to  the  spine  of  the  pubic  bone.  It  is 
the  lower  border  of  the  aponeurosis  of  the  external  oblique  muscle  of 
the  abdomen. 

Pretracheal.    In  front  of  the  trachea. 

Prevertebral.    In  front  of  the  vertebral  column. 

Proligerous  (disk).  (From  the  Latin  word  proles,  "ofifspring;" 
gere,  "to  bear.")  Producing  offspring.  The  layer  of  cells  in  the 
membrana  granulosa  of  the  Graafian  follicle  that  surrounds  the  ovum. 

Pronation.  (From  the  Latin  word  pronare,  "to  bend  forward.") 
The  act  of  turning  the  palm  downward;  the  opposite  of  supination. 

Pronator  Quadratus  (muscle).    Square  pronator.    See  pronation. 

Pronator  Radii  Teres  (muscle).    The  round  pronator  of  the  radius. 

Protein  or  Proteid.  Any  one  of  the  important  and  essential  con- 
stituents of  animal  and  vegetable  tissues  containing  nitrogen. 

Proteolysis.  The  change  produced  in  proteins  or  proteids  by  fer- 
ments that  convert  them  into  diffusible  bodies. 

Proteolytic  Ferments.  Pertaining  to  those  ferments  which  are 
characterized  or  effect  proteolysis. 

Proteose.  Any  one  of  a  group  of  bodies  formed  in  gastric  digestion 
intermediate  between  the  food  proteins  and  peptones,  called  anti- 
peptones,  hemipeptones. 

Protoplasm.  The  viscid  material  constituting  the  essential  sub- 
stance of  living  cells,  upon  which  all  the  vital  functions  of  nutrition, 
secretion,  growth,  reproduction,  irritability,  motility  depend. 

Proximal.  (From  the  Latin  word  proximus,  "  the  nearest.")  Nearest 
to  the  body,  or  the  median  line  of  the  body.  Proximal  phalanx:  The 
nearest  bone  of  the  finger. 

Proximate  (principles).  (From  the  Latin  word  proximus,  "nearest.") 
Nearest.  Proximate  principles,  substances  which  can  exist  under 
their  own  form  in  the  animal  solids  or  fluids,  and  that  can  be  extracted 
by  means  not  altering  or  destroying  their  chemic  properties. 

Pterygoid.    Wing-shaped. 

Puberty.  From  the  Latin  word  pubertas,  from  puber,  "adult.") 
The  period  at  which  the  generative  organs  become  active  in  both 
sexes,  and  become  capable  of  reproduction. 

Pubes.    The  hairy  region  covering  the  os  pubis  (pubic  bone). 

Pubic.     Pertaining  to  the  pubes. 

Pubis  (Os).  The  bone  of  the  pubes.  The  lower  and  anterior  part 
of  the  innominate  bone. 

Pyloric.  Pertaining  to  the  pylorus  of  the  stomach,  as  pyloric  artery, 
vein,  etc. 

Pylorus.  (From  the  Greek  word  meaning  gate-keeper.)  The 
circular  opening  of  the  stomach  into  the  duodenum. 

Pyramidal.    Shaped  like  a  pyramid. 

Pyramidalis  (muscle).  The  muscle  shaped  like  a  pyramid  found 
at  the  lower  part  and  inserted  into  the  linea  alba  of  the  abdominal 
wall.    There  are  two. 

Pyramidalis  Nasi  (muscle).    The  pyramidal  one  of  the  nose. 

Quadratus.    Squared;  four-sided. 


GLOSSARY  453 

Quadrangular.    Having  four  angles. 

Quadriceps  (extensor  tendon).    The  four-headed  extensor  tendon. 

Racemose.  (From  the  Latin  word  racemus,  "a  bunch  of  grapes.") 
Resembling  a  bunch  of  grapes. 

Radius  (bone).  (From  the  Latin  word  radius,  "the  spoke  of  a 
wheel.")    The  outer  bone  of  the  forearm. 

Rami  Communicantes.  (From  the  Latin  words  ramus  (pi.  i),  "a 
branch;"  communicans  (pi.  antes),  "communicating.")  Communi- 
cating branches.  The  branches  of  a  spinal  nerve  connecting  it  with 
the  sympathetic  ganglia. 

Reflex  (action).  (From  the  Latin  words  re,  "back;"  flectere,  "to 
bend.")  Anything  bended  or  thrown  back.  Reflex  act:  An  act 
following  immediately  upon  a  stimulus  without  the  intervention 
of  the  will. 

Refractory  (apparatus).  (From  the  Latin  words  re,  "back;"  fran- 
gere,  "to  break.")  Literally,  to  break  the  natural  course  of,  as  rays 
of  light;  to  cause  them  to  deviate  from  a  direct  course,  as  the  refractory 
apparatus  of  the  eye  deviates  the  rays  of  light  as  to  how  they  shall 
fall  upon  the  retina  (diffuse  or  concentrated),  based  upon  the  nearness 
or  distance  of  an  object  to  or  from  the  eye. 

Renal.  (From  the  Latin  word  ren,  "a  kidney.")  Pertaining  to 
the  kidney. 

Renalis  (fascia).    Fascia  of  the  kidney. 

Renes  (pi,  of  ren.).    The  kidneys. 

Reniform.    Kidney-shaped. 

Reticular.  (From  the  Latin  word  reticulum,  dim.  of  rete,  "a  net.") 
Resembling  a  net,  formed  by  a  net-work,  as  reticular  tissue. 

Reticulum.    A  net-work. 

Retiform.    Having  the  form  of  a  net. 

RhythmicaL  Pertaining  to  rhythm.  In  speaking  of  the  heart  and 
pulse  it  refers  to  the  dividing  of  their  actions  (contraction  and  relaxa- 
tion) into  short  portions  or  periods  by  a  regular  succession  of  motions. 

Rima  Glottidis.  The  chink  of  the  glottis.  The  cleft  or  narrow 
opening  between  the  true  vocal  cords  in  the  larynx. 

Risorius  (muscle).  (From  the  Latin  word  ridere,  "to  laugh.") 
The  laughing  muscle. 

Rotation.  (From  the  Latin  words  rotare,  "to  turn;"  from  rota,  "a 
wheel.")  The  act  of  turning  about  an  axis,  passing  through  the  centre 
of  a  body  or  extremity. 

Rugae,     (Plural  of  ruga,  "a  fold  or  ridge.")    Folds. 

Saccharoses.  (From  the  Greek  word  meaning  sugar.)  A  group  of 
carbohydrates  occurring  in  the  juice  of  many  plants,  chiefly  sugar-cane, 
some  varieties  of  maple  and  beet-sugar. 

Sacrum  (bone).  (From  the  Latin  word  sacer,  "sacred;"  os,  under- 
stood.) 

Sagittal.  (From  the  Latin  word  sagitta,  "an  arrow,")  Arrow-like, 
as  the  sagittal  suture  of  the  skull.  Referring  to  the  anteroposterior 
middle  plane  of  the  body,  or  organ,  etc. 

Saphenous.  Apparent,  superficial;  applied  to  the  saphenous  vein 
of  the  thigh  and  leg,  lying  just  beneath  the  skin  and  superficial 
fascia. 

Sarcolemma.    The  delicate  membrane  enveloping  a  muscle  fiber. 


454  GLOSSARY 

Sarcoplasm.  The  finely  granular  material  between  the  fibrils  of 
muscle  tissue. 

Sartorius  (muscle).  (From  the  Latin  word  sartor,  "a  tailor.") 
The  tailor  muscle.  Named  after  the  ancient  method  the  tailor  assumed 
while  at  work,  squatting  with  his  knees  bent,  and  the  feet  and  leg 
crossed. 

Scaphoid  (bone).    Boat-shaped.    A  bone  of  the  wrist  and  instep. 

Scapula  (bone).    (From  the  Latin.)    A  shoulder-blade. 

Secretion.  (From  the  Latin  word  secernere,  'Ho  secrete,  separate.") 
1.  The  act  of  secreting  or  forming  from  materials  furnished  by  the 
blood  a  certain  substance  which  is  either  eliminated  by  the  body  or 
is  used  in  carrying  on  certain  fimctions.  2.  The  substance  secreted, 
as  bile,  sweat,  etc. 

Secretor  or  Secretory.  Pertaining  to  or  performing  secretion  of  a 
gland,  etc. 

Sella  Turcica.  (A  Turkish  saddle.)  The  pituitary  fossa  of  the 
body  of  the  sphenoid  bone,  lodging  the  pituitary  body. 

Semilunar.  (From  the  Latin  words  semi,  ''half;"  luna,  "moon.") 
Resembling  a  half-moon  in  shape. 

Semimembranosus  (muscle).    Half-membrane. 

Semitendinosus  (muscle).    Half -tendon. 

Septum  (pi.  septa).  (From  the  Latin  word  sepire,  "to  hem  in.") 
A  partition,  a  dividing  wall,  as  nasal  septum,  etc. 

Sensor  or  Sensory.  (From  the  Latin  word  sentire,  "to  feel.") 
Pertaining  to  or  conveying  sensation,  as  a  sensor  nerve. 

Serous  (membrane).    Pertaining  to  or  resembling  serum. 

Serum.  (From  the  Latin  word  serum,  "serum.")  L  The  clear, 
yellowish  fluid  separating  from  the  blood  after  the  coagulation  of  the 
fibrin.    2.  Any  clear  fluid  resembling  the  serum  of  the  blood. 

Sigmoid.    Shaped  like  the  Greek  letter  2. 

Sinus.    A  hollow  or  cavity. 

Soleus  (muscle).    A  flat  muscle  of  the  calf. 

Solitary.  (From  the  Latin  word  sohtarius,  "soHtary.")  Single, 
existing  separately. 

Specific  Gravity.  The  measured  weight  of  a  substance  compared 
with  that  of  an  equal  volume  of  another  taken  as  a  standard. 

Sphenoid.    Wedge-shaped. 

Spheric.    Having  the  shape  of  a  sphere. 

Sphincter.  A  muscle  surrounding  and  closing  an  orifice;  as  sphincter 
ani  muscle. 

Spicule.    A  minute,  sharp-pointed  body,  as  a  spicule  of  bone. 

Spinal  (nerve).  1.  Pertaining  to  the  spine.  2.  Pertaining  to  the 
spinal  cord. 

Spinus.  (From  the  Latin  word  spina,  "a  spine  or  thorn.")  Resgm- 
bling  or  pertaining  to  a  spine. 

Squamous.  (From  the  Latin  word  squamosis,  "scaly.")  Of  the 
shape  of  a  scale. 

Stellate.     (From  the  Latin  word  stella,  "a  star.")    Star-shaped. 

Sternohyoid  (muscle).    From  the  sternum  to  the  hyoid  bone. 

Sternomastoid  (muscle).    From  the  sternum  to  the  mastoid. 

Sternothyroid  (muscle) .    From  the  sternum  to  the  thyroid  cartilage. 

Sternum.    Breast  bone. 


GLOSSARY  455 

Stratified.  (From  the  Latin  word  stratum,  "a  layer;"  facere,  "to 
make.")    Formed  into  a  layer  or  layers. 

Stratum  Germinatum.    The  sprouting  layer  (skin). 

Stratum  Granulosum.    The  granular  layer  (skin). 

Stratum  Lucidum.    The  clear  layer  (skin) . 

Stratum  Mucosum.    The  mucous  layer  (skin). 

Striated.    Striped. 

Stroma.  The  tissue  forming  the  frame-work  for  the  necessary  part 
of  an  organ  or  tissue. 

Stylohyoid.  Pertaining  to  the  styloid  process  of  the  temporal  bone 
and  the  hyoid  bone. 

Styloid.    Resembling  a  pillar. 

Sub.    A  prefix  denoting  under  or  beneath. 

Subaponeurotic.    Beneath  the  aponeurosis. 

Subclavian.    Beneath  the  clavicle. 

Subclavius  (muscle) .     Beneath  the  clavicle. 

Subcostal.    Beneath  a  rib. 

Subcutaneous.    Beneath  the  skin. 

Subendothelial.    Beneath  the  endothelium.    (See  endothelium.) 

Subpubic.    Beneath  the  symphysis  pubes. 

Sulcus.    A  furrow  or  groove.     (From  the  Latin  ) 

Sulcus  PulmonaUs.    The  groove  of  the  lung. 

Superciliary.  (From  the  Latin  words  super,  "above;"  cilium,  "an 
eyelash.)    Pertaining  to  the  eyebrow. 

Supination.  (From  the  Latin  word  supinus,  "on  the  back.")  The 
act  of  turning  the  palm  of  the  hand  upward.  The  condition  of  being 
on  the  back.    Opposite  of  pronation. 

Supinator  Brevis  (muscle).  The  short  supinator  (assists  to  turn  the 
palm  upward). 

Supinator  Longus  (muscle).  The  long  supinator  (assists  to  turn 
the  palm  upward). 

Supracondylar.    Above  the  condyle. 

Suprapatellar.    Above  the  patella. 

Suprarenal.    Above  the  kidney. 

Sutural.  (From  the  Latin  word  sutura,  "a  suture;"  from  sutere, 
"to  sew  or  stitch.")    Pertaining  to  suture. 

Suture.  A  suture.  The  seam  or  joint  which  unites  the  bones  of 
the  skull. 

Symphysis  (pubes).  The  line  of  junction  of  two  bones  Sym- 
physis pubis:  The  line  of  junction  of  the  two  bodies  of  the  pubic  bones 
located  at  the  front  of  the  true  pelvis. 

Synarthrosis.  A  form  of  joint  or  articulation  in  which  the  bones 
are  firmly  bound  together  and  are  immovable.  They  have  no  synovial 
membrane. 

Synchondrosis.  A  joint  in  which  the  surfaces  of  bones  are  connected 
by  a  cartilage. 

Syndesmosis.  A  form  of  joint  in  which  the  bones  are  held  together 
by  ligaments. 

Synovia.  The  clear,  alkaline,  lubricating  fluid  secreted  by  the  cells 
of  a  synovial  membrane,  found  within  a  synovial  sac. 

Synovial.    Pertaining  to  the  synovia. 


456  GLOSSARY 

Systole.  (From  the  Greek  words  together,  to  place.)  The  con- 
traction of  the  heart  muscle.  Auricular  systole,  the  contraction  of 
the  auricle  of  the  heart;  ventricular  systole,  the  contraction  of  the 
ventricle  of  the  heart. 

Tactile.  (From  the  Latin  word  tactus,  from  tangere,  "to  touch.") 
Pertaining  to  the  sense  of  touch. 

Tarsus.    The  instep. 

Temporal  (bone).  (From  the  Latin  word  tempus,  "time  (temple).") 
Pertaining  to  the  temple,  as  temporal  bone,  artery,  etc. 

Tendo  Achillis.  The  tendon  of  Achilles.  (Tendon,  from  the  Latin 
word  tendere,  "to  stretch.")  The  common  tendon  of  the  gastrocne- 
mius and  soleus  muscles. 

Tendo  Oculi.    The  tendon  of  the  eyeball. 

Tensor  Vaginae  or  Fasciae  Femoris.  The  stretcher  of  the  sheath 
(fascia  lata)  of  the  thigh. 

Tentorium  Cerebelli.  The  tent  of  the  cerebellum.  The  partition 
of  dura  mater  between  the  cerebrum  and  cerebellum. 

Thenar.  (From  the  Greek  word  meaning  palm.)  1.  The  palm  of 
the  hand.  2.  The  fleshy  prominence  of  the  palm  corresponding  to  the 
base  of  the  thumb;  also  called  thenar  eminence  (ball  of  the  thumb). 

Thermal.    Pertaining  to  heat. 

Thermic.    Pertaining  to  heat. 

Thoracic.    Pertaining  to  or  situated  in  the  thorax  or  chest. 

Thorax.    From  the  Greek  word  meaning  chest. 

Thyrohyoid  (muscle).  From  the  thyroid  cartilage  to  the  hyoid  bone, 
as  thyrohyoid  muscle  and  membrane. 

Thyroid.  Shield-shaped.  Pertaining  to  the  thyroid  gland,  cartilage, 
etc. 

Tibia  (bone).  (From  the  Latin  word  tibia,  "a  shin.")  The  large 
bone  on  the  inner  side  of  the  leg. 

Tibiofibular  (articulation).    Pertaining  to  the  tibia  and  fibula. 

Tissue.  (From  the  Latin  word  texere,  "to  weave.")  An  arrange- 
ment of  similar  cells  and  fibers,  forming  a  distinct  structure,  and 
entering  as  such  into  the  formation  of  an  organ  or  organism. 

Tonicity.  The  condition  of  normal  tone  or  tension  of  organs;  a 
state  of  tone. 

Tonus.    The  normal  state  of  tension  of  a  part  or  of  the  body. 

Trabecula  (pi.  se).  (From  the  Latin  word  trabecula,  "a  small 
beam.")  Any  one  of  the  fibrous  bands  extending  from  the  capsule 
into  the  interior  of  an  organ. 

Trachea.    Windpipe. 

Transitional.    Denoting  a  change  from  one  shape  to  another. 

Trapezium  (bone).  (Named  after  the  resemblance  it  bears  to  a 
trapezium;  shaped  like  an  irregular  four-sided  figure.)  The  first 
bone  of  the  second  row  of  the  wrist. 

Trapezius  (muscle).    Resembles  a  trapezium  in  shape. 

Trapezoid  (bone).  Resembles  a  trapezoid— a  four-sided  geometric 
figure  having  two  parallel  and  two  diverging  sides. 

Triceps  (muscle).    Three-headed. 

Tricuspid.    Having  three  cusps  or  points. 

Trochanters.    The  processes  on  the  upper  extremity  of  the  femur. 

Trochlear.    Pertaining  to  or  having  the  nature  of  a  pulley. 


GLOSSARY  457 

Trophic.  (From  the  Greek  word  meaning  nourishment.)  Pertaining 
to  nutrition.  Trophic  centre,  a  collection  of  ganglion  cells  regulating 
the  nutrition  of  a  nerve,  and  thus  through  the  latter  the  part  it 
supplies. 

Tuber  Cinereum.  A  tract  of  gray  matter  at  the  base  of  the  cere- 
brum, extending  from  the  optic  chiasm  to  the  corpora  mammillaria,  and 
forming  part  of  the  floor  of  the  third  ventricle. 

Tuberculum  or  Tubercle.  (From  the  Latin  word  tuberculum,  "a 
tubercle.")    A  small  nodule.'  A  rounded  prominence  on  a  bone. 

Tuberosity.  (From  the  Latin  word  tuber,  "a.  swelling.")  A  pro- 
tuberance on  a  bone. 

Tubular.  From  the  Latin  word  tubulus,  a  dim.  of  tubus,  "a  tube.") 
Shaped  like  a  tube.    Pertaining  to  a  tube. 

Tubule.    From  the  Latin  word  tubulus,  "a  small  tube." 

Tunica.  (From  the  Latin  word  tunica,  ''tunic")  A  coat  or  mem- 
brane. 

Tunica  Adventitia.    The  outer  coat  of  an  artery  or  vein. 

Tunica  Intima.    The  inner  coat  of  an  artery  or  vein. 

Tunica  Media.    The  middle  coat  of  an  artery  or  vein. 

Tympanic  (membrane).    Pertaining  to  the  tympanum. 

Tympanum.  (From  the  Greek  word  meaning  *'a  drum.")  The 
middle  ear. 

Ulna  (bone).  (From  the  Latin  word  ulna,  "a  cubit.")  The  bone 
on  the  inner  side  of  the  forearm. 

Unciform  (bone).  (From  the  Latin  word  uncus,  "a  hook;"  forma, 
"form.")  Hook-shaped.  A  hook-shaped  bone  in  the  second  row  of 
the  wrist. 

Unipolar.  (From  the  Latin  words  unus,  "one;"  polus,  "a  pole.") 
Having  but  one  pole  or  process.    As  a  unipolar  nerve  cell. 

Urea.  The  chief  nitrogenous  constituent  of  the  urine,  and  principal 
end-product  of  tissue  metabolism. 

Uriniferous  (tubules).  (From  the  Latin  words  urina,  "urine;"  ferre, 
"to  bea/.")  The  tubules  which  carry  or  convey  urine  from  the  kidney 
substance  to  the  pyramids  of  the  kidney. 

Uvula.  (From  the  Latin  word  uvula,  from  the  dim.  of  uva,  "a 
grape.")  The  cone-shaped  appendage  hanging  from  the  free  edge  of 
the  soft  palate. 

Vagina.  (From  the  Latin  word  vagina,  "a  sheath.")  1.  A  sheath. 
2.  The  musculomembranous  canal  extending  from  the  vulval  opening 
to  the  mouth  of  the  cervix  of  the  uterus  (ostium  externum),  ensheathing 
the  latter  and  the  penis  (male)  during  coitus.     (See  Coitus.) 

Vaginal.  1.  Pertaining  to  or  of  the  nature  of  a  sheath.  2.  Relating 
to  the  vagina. 

Valvulae  Conniventes.  The  small  transverse  folds  of  mucous  mem- 
brane of  the  small  intestine. 

Vasa  Brevia.  The  short  vessels.  The  small  branches  of  the  splenic 
artery  which  pass  to  the  fundus  of  the  stomach. 

Vasoconstrictor  (nerves).  (From  the  Latin  words  vas,  "vessel;" 
constringere,  "to  constrict.")  Nerves  which  when  stimulated  cause 
a  contraction  of  the  bloodvessels. 

Vasodilator.  (From  the  Latin  words  vas,  "a  vessel;"  dilator,  "a 
dilator.")  Nerves  which  when  stimulated  cause  a  dilatation  of  the 
bloodvessels. 


458  GLOSSARY 

Vasomotor.  (From  the  Latin  words  vas,  "a.  vessel;"  motor,  from 
movere,  "to  move."    Regulating  the  tension  of  the  bloodvessels. 

Venae  Cavse.  (LiteraUy,  the  hollow  veins.)  The  two  large  veins 
that  open  into  the  right  auricle  of  the  heart. 

VensB  Comites.  (Accompanying  veins.)  Veins  that  accompany  an 
artery  in  its  course. 

Venae  Cordis  Minimi.    The  smallest  veins  of  the  heart. 

Ventral.  (From  the  Latin  word  venter,  "belly.")  Pertaining  to 
the  belly.    Or  used  in  meaning  in  front,  as  ventral  aspect. 

Ventricle.  A  small  cavity  or  pouch.  (From  the  Latin  ventriculus, 
a  dim.  of  venter,  "a  belly.") 

Venule.    A  small  vein. 

Vermiform  (appendix).  (From  the  Latin  word  vermis,  "a,  worm;" 
forma,  "form.")    Worm-shaped  appendix. 

Vemix  Caseosa.  (A  cheesy  varnish.)  The  sebaceous  deposit 
covering  the  surface  of  the  fetus.    Seen  on  delivery. 

Vertebra.  (From  the  Latin  word  vertere,  "to  turn."  A  single  bone 
of  the  spinal  column. 

Vertebral.    Referring  to  or  characteristic  of  the  vertebra. 

Vertex.  (That  which  turns  or  revolves  about  itseK,  from  the  Latin 
word  vertere,  "to  turn.")    The  crown  or  top  of  the  head  or  skull. 

Vesica  Urinaris.    The  urinary  bladder. 

Villus  (pi.  villi).  (From  the  Latin  word,  "a  tuft  of  hair.")  The 
minute  club-shaped  projections  from  the  mucous  membrane  of  the 
small  intestine,  consisting  of  a  lacteal  vessel,  an  arteriole,  and  a  venule, 
enclosed  in  a  layer  of  epithelial  cells. 

Virgin.    A  woman  who  has  never  had  sexual  intercourse. 

Viscera     Plural  of  viscus,  meaning  the  organs  of  the  abdomen,  etc. 

Visceral.    Relating  to  viscera,  the  stomach,  liver,  etc. 

Vitreous  (humor).  (From  the  Latin  word  vitreus,  from  vitrum, 
"glass.")  The  transparent,  jelly-like  substance  filling  the  posterior 
chamber  of  the  eye. 

Volatile.  (From  the  Latin  word  volatilis,  from  volare,  "to  fly.") 
Passing  into  vapors  at  ordinary  temperatures;  evaporating. 

Voluntary.    Under  the  control  of  the  will.    Voluntary  muscles,  etc. 

Vomer.  (From  the  Latin,  "a  ploughshare.")  The  thin  plate  of  bone 
situated  vertically  between  the  nasal  cavities,  which  forms  the  posterior 
portion  of  the  nasal  septum  (partition). 

Vulva.  (From  the  Latin  word  volvere,  "to  roll  up.")  The  external 
organs  of  generation  in  the  woman. 

Zygoma.  (From  the  Greek  word  meaning  cheek  bone.)  The  bony 
arch  above  the  cheek  and  in  front  of  the  ear  formed  by  the  zygomatic 
processes  from  the  temporal  and  malar  bones. 

Zygomatic.    Relating  to  the  zygoma. 


INDEX 


Abdomen,  18 

fascia  of,  144 

regions  of,  264.     See  Fig.  102. 
Abdominal   aorta,    192,   202 
branches  of,  192,  202 

regions,  264.     See  Fig.   102 
Abducens  nerve  (sixth),  375 
Abduction,  113,  158 

of  joint,  113 
Abductor    hallucis    muscle,    245, 
246 

of  little  finger,   157 
toe,  171 

minimi  digiti,  157 

poUicis,  157 
Absorption,  286 

of  food,  286 

of  lymph,  286 

of  products  of  digestion,  287 

relation  of  villi  to,  286,  287 
Absorptive  apparatus,  286 
Accessorius  muscle,  action  of,  171 
Accessory  organs  of  digestion,  251 
Accommodation,  404 
Acetabulum,  93,  97 
Acromegalia,  308 
Acromial  process,  84 
Addison's  disease,  307 
Adduction,  ,113,  158 

in  joint,  113 
Adductor  brevis  piuscle,  166 

hallucis,    171 

longus,  164 

magnus,  166 

obliquus  hallucis,  171 
pollicis,  157 

transversus  hallucis,  171 
pollicis,  157 
Adipose  or  fatty  tissue,  50 
Adrenal  gland,  307 
Air,  relation  to  respiration,  247 

sacs,  244 
Albumen,  24 

varieties  of,  24 


Albuminoids,  24 

compounds  of,  25 

varieties  of,  24 
Alimentary  canal,  251 

divisions  of,  251,  252 
Alveolar  glands,  45 
Alveoli  of  lungs,  244 
Ameboid  movement  of  cells,  33 

white  cells  in  blood,  33,  220 
Amphiarthrosis,  109 
Ampulla  of  breast,  293 

of  vater,  302 
Amyelinic  nerve  fibers,  334,  335 
Amylopsin,    280 

action   in   intestinal   digestion, 
280 
Amyloses,  21 
Anabolism,  29 
Anastomosis.    See  Glossary. 
Anatomy,  description  of,  circula- 
tory apparatus,  174 

and   physiology   of    the  nerve 
system,  331 

urinary  apparatus,  314 
Anconeus  muscle,  155 
Angiology,  definition  of,  18 
Angular  movements   in   a  joint, 

112,  113 
Animal  starch,  21 
Annular  ligaments,  124,  155 
Anterior  chamber  of  eye-ball,  401 

columns  of  spinal  cord,  347 
horns  of,  348 

tibial  artery,  208 
Antrum  of  Highmore,  72,  395 
Aorta,  192 

abdominal,  192,  202 

arch  of,  192 

ascending,  192 

branches  of  abdominal,  203 
of  arch,  194 
of  thoracic,  202 

descending,  192,  194 

thoracic,  192,  202 

transverse,  192,194 
Aponeurosis,  122,  123 


460 


INDEX 


Aponeurosis,  composition  of,  122, 
123 

function  of,  123 
Appendages  of  eye,  397 

of  hairs,  325 

of  nails,  325 

of  sebaceous  glands,  325,  326 

of  skin,  325 

of  sweat  glands,  325,  327 
Appendicular  portion  of  body,  18 
Appendix  vermiformis,  269 
Aqueous  humor  of  eye-ball,  401 
Arachnoid    membrane    of    brain, 
355 

of  spinal  cord,  346 
Arbor  vitae  of  cerebellum,  358 

of  uterus,  422 
Arch  of  aorta,  192 
Areola  of  breasts,  293 
Areolar  tissue,  50 
Arm,  arteries  of,  198 

bones  of,  85 

muscles  of,  149 

veins  of,  213 
Arrangement  (anatomic)  of  body 

as  a  whole,  17 
Artefacts,  47 
Arterial  system,  191 
corporeal,  192 
pulmonary,  192 
Arteries,  185,  186 

anastomosis  of.     See  Glossary. 

axillary,  198 

basilar,  197 

blood-pressure  of,  190,  191 

brachial,  198 

bronchial,  202 

carotid,  common,  194 
external,  194 
internal,  194 

celiac  or  coeliac  axis,  203 

circle  of  Willis,  198 

coats  of,  186 

contractility  of,  186 

coronary,  194 

cystic,  203 

description  of,  191 

distribution  of,  191 

elasticity  of.  186 

esophageal  or  oesophageal,  202 

facial,  195.    See  Fig.  76. 

femoral,  206 

function  of,  185 

gastric,  203 

gastroduodenal,  203 

gastroepiploica,  204 
dextra  (right),  203 
sinistra  (loft),  204 

hemorrhage  from,  191 


Arteries,  hemorrhoidal,  206 
hepatic,  203 
iliac,  common,  205 

external,  205,  206 

internal,  205 
innominate,  194 
intercostal,  202 
internal  pudic,  206 
of  lower  extremity,  206 

upper,  198 
lumbar,  203 
mediastinal,  202 
mesenteric,  inferior,  205 

superior,  205 
middle  sacral,  203 
muscle  tissue  in  wall,  186 
nerve  supply  of,  187 
oesophageal,  202 
obturator,  202 
ovarian,  205 
palmar  arches  of  hand,  198,  201 

deep,  198,  201 

superficial,  198,  201 
pancreaticoduodenal,  204 
pericardial,  202 
phrenic,  203 
plantar,  208 

arch,  208 
popliteal,  208 
pulmonary,  178,  192 
pyloric,  203 
radial,  198 

relations  of,  198 
renal,  205 
sciatic,  206 

spermatic  (in  male),  205 
splenic,  203 
structure  of,  185 
subclavian,  196 
suprarenal,  205 
tibial,  anterior,  208 

posterior,  208 
ulnar,  199 
uterine,  206 
vaginal,  206 

vasae  brevise  of  splenic,  204 
vesical,  inferior,  206 

superior,  205 
Arterial  tension,  190 
Arterioles,  188 

Arthrodial  joint,  108.     See  Table. 
Articular  surfaces  of  bones,  56 
Articulate  speech,  238 
Articulations  of  joints,  106 

bones  in,  106 

cartilage  in,  106 

general  structure  of,  106 

ligaments  of,  106 

synovial  membranes  in,  106 


INDEX 


461 


Articulations  of  joints,   table  of  [ 

classification,  108  i 

Arytenoid  cartilage,  236  i 

Atlas  (bone) ,  77  j 

Atrioventricular  bundle  (His),  181  | 
Auditory  apparatus,  407  j 

anatomy  and  phj^siology  of, 
407 

canals,  external,  407 

nerve,  377 

ossicles,  410 
Auricle  of  heart,  left,  179 
right,  176 

or  pinna  of  ear,  407 
Axial  portion  of  body,  17 
Axillary  artery,  198 

fascia,  143 

vein,  213 
Axis  (bone),  78 

Axis-cylinder  of  nerve  cell,  333 
Axone  of  nerve  cell,  333 

varieties  of,  334. 


Back,  muscles  of,  137 
Bartholin's  duct,  258 

gland  of,  419 
Basilar  artery,  197 
Basilic  vein,  213 
Beet-sugar,  22 
Biceps  muscle  of  arm,  149 

of  thigh,  164 
Bicuspid  or  mitral  valve  (heart), 

179 
Bile,  281 

composition  of,  281 

duct,  common,  281 

ducts,  281 

function  of,  281 

part   played    by,  in    digestion, 
281 

secretion  of,  281 

s'tored  in  gall-bladder,  28ri 
Bipolar  nerve-cell,  333 
Bladder,  capacity  of,  318 

dimensions  of,  318 

urinary,  318 
Blastodermic  vesicle,  40 
Blastula,  40 
Blood,  217 

changes  occurring  in  lungs,  217, 
220 
in  tissues,  217,  220 

characteristics  of,  physical,  217 

circulation  of,  180 

clotting  of,  222 

coagulation,  222 


Blood,  constituents  of,  217 
defibrinated,  222 
effect  of  carbon  dioxide  upon, 
217,  220 
of  oxygen  upon,  217,  220 
of  respiration  upon,  180, 
220,  247 
fat  in,  218 
fibrin  in,  218,  222 
fibrinogen  in,  218,  222 
functions  of,  217 
hemoglobin  in,  217 
paraglobulin  in,  218 
"peripheral  resistance  of,  191 
plaques,  217,  222 
plasma,  217 
pressure,  190 

of  arteries,  190,  191 
of  capillaries,  191 
definition  of,  190 
of  veins,  191 
proteins  in,   218 
reaction  of,  217 
red  cells  in,  217,  219 
salts  in,  219 
serum,  218 

albumin,  218 
sugar  in,  218 
white  cells  in,  217,  220 
Blood  cells  or  corpuscles,  219,  220 
composition  of,  219 
red,  217,  219,  220 

effect  of  respiration  upon, 

219,  247 
functions  of,  219 
hemoglobin  in,  217,  219 
number  of,  219 
white,  220 

ameboid  movement  of,  220 
functions  of,  221 
number  of,  220 
phagocytosis  of,  221 
varieties  of,  221 
Blue  baby,  185 

Body,  composition  of,  inorganic, 
20,  25 
organic,    20 
divisions  of,  17 

appendicular  portion,  18 
axial  portion,  17 
dorsal  cavity  of,  17 
ventral,  18 
heat,  310 

dissipation,  311,  312 
production,  310 
regulation,  310 
temperature,  310,  312 
Bone  or  bones,  54 
astragalus,  102 


462 


INDEX 


Bone  or  bones,  atlas,  77 
axis,  78 

blood-supply  of,  57,  58 
calcaneum  or  os  calcis,  102 
canaliculi  in,  58 
cancellous,  58 

carpal,   articulations  of,   90 
classification  of,  54 
clavicle,    84 
coccyx,  79 
compact,  58 
composition  of,  57 
cuneiform,  91 
depressions  in,  articular,  56 

non-articular,    56 
diaphysis  of,  55 
digifS  of  hand,  92 

of  foot,  104 
eminences  of,  articular,  56 

non-articular,  56 
endosteum  of,  58 
epiphysis  of,  55 
ethmoid,  65 
femur,  97 

fibers  of  Sharpey  in,  58 
fibula,  102 
fiat,  55 
frontal,  61 
functions  of,  54 
green-stick  fracture  of,  57 
Haversian  canals  in,  58 

system  in,  59 
Howship's  fovea,  58 
humerus,  85 
hyoid,  68 
ilium,  93 

incus  (ossicle),  410 
inorganic  constituents,  57 
irregular,  56 
ischium,  93 
lacrymal,  67 
lacuna  of,  58 
long,  54 
lower  jaw,  68 
malar,  68 
malleolus  of  fibula,  102 

tibia,  101 
malleus  (ossicle),  410 
mandible,  68 
marrow,  59 

cells,  59 
maxilla,  67 
medullary  canal,  55,  59 

endosteum  of,  58 
metacarpal,  92 
metatarsal,  104 
nasal,  66 
number  of,  55 
occipital,  60 


Bone  or  bones  of  arm,  85 
of  carpus,  90 
of  cranium,  60 
of  ear  (ossicles),  410 
of  face,  60,  66 
of  foot,  102 
of  forearm,  87 
of  hand,  92 
of  head,  59 
of  hip,  97,  98 
of  instep,  102 
of  legs,  99 

of  lower  extremity,  93 
of  metacarpus,  92 
of  metatarsus,  104 
of  orbital  cavity,  71 
of  pelvis,  93 
of  tarsus,  102 
of  thigh,  97,  98 
of  thorax,  79,  80 
of  upper  extremity,  84 
of  wrist,  90 

organic  constituents  of,  57 
OS  magnum,  91 
OS  pubis,  93 
osteoblasts  in,  57 
osteoclasts,  58 
palate,  68 
parietal,  60 

patella  or  knee-cap,  99 
pelvis  as  a  whole,  93 
periosteum  of,  57 
phalanges  of  foot,  104 

of  hand,  92 
pisiform,  91 
pubes,  symphysis,  93 
pubic,  93 
radius,  89 
rib  or  ribs,  82 

peculiar,  83 

typical,  82 
sacrum,  79 
scaphoid,  91 
scapula,  84 
semilunar,  91 
Sharpey's  fibers  in,  58 
short,  55 
skin,  101 

skull  as  a  whole,  69 
solid,  58 
sphenoid,  65 
spongy,  58 
stapes  (ossicle),  410 
sternum,  82 
surfaces  of,  56 
table  of  cranial,  60 

face,  60 
tarsal,  102 
temporal,  62 


INDEX 


463 


Bone  or  bones,  thorax,  as  a  whole, 
79 

tibia,  99 

trapeziod,  91 

trapezium,  91 

turbinated,  68 

ulna,  87 

unciform,  91 

upper  jaw,  67 

vertebra  or  vertebrse,  76 

general  characteristics  of,  75 

vertebral  column  as  a  whole,  72 
divisions  of  bones  of,  72 

Volkmann's  canals,  58 

vomer,    66 
Brachial  artery,  198 

plexus  of  nerves,  380 
Brachium.    See  Glossary. 
Brachialis  anticus  muscle,  149 
Brain,  354 

areas  of,  364,  365,  366 

arteries  of,  197,  198 

convolutions   of,   359,   360 

divisions  of,  354,  355 

fissures  of,  359,  360 

functions,  localizations  of,  364, 
365 

lobes  of,  361 

membranes  of,  354 

motor  area  in,  364 

nerves  of  (cranial),  368 

sensor  areas  in,  366 

ventricles  of,  362 

weight  of,  female,  364 
male,  364 
Breast  bone  (sternum),  82 
Breathing  air  into  lungs,  245 
Broad  ligaments  of  uterus,  422 
Bronchial  artery,  202 

tubes,  240 
Bronchus  or  bronchi,  240 

structure  of,  240 
Bronchioles,  244 
Brunner's  glands,  267 
Buccinator  muscle,  131 
Bursse.  mucous,  107 

synovial,  107,  292 


Cachexia  strumipriva,  305 

Calcaneum  (bone),  102 

Calices  of  kidney,  316,  318 

Calorie,  definition  of,  30 

method  of  determination,  312 
table  of,  derived  from  diet,  311 

Canal,  alimentary,  251 
auditory,  external,  407 


Canal,  medullary  of  bone,  58 

spinal,  74,  346 
Cancellous  bone,  58 
Cane-sugar,  22 
Canine  teeth,  252 
Canthi  of  eye,  397 
Capacity  of  bladder,  318 

lungs,  vital,  246 

stomach,  adult,  236 
infant,  283 
Capillary  or  capillaries,  188 

blood-pressure  in,  191 

circulation,  188 

coats  of,  188 

function  of,  188 

size  of,  188 

structure  of,  185,  188 
Capsule  of  Glisson,  298 

of  Tenon,  396 
Carbohydrates,  20 

composition  of,  21 
Carbon  dioxide.     See  Glossary, 
absorbed    from    tissues,    180 

220 
effect  upon  blood,  217,  220 
given  off  by  lungs,  180,  220 
Cardiac  cycle,  183 

nerve,  accelerator,  387 

inhibitor,  387 
sinus  of,  177,  211 
time  of  divisions  of,  183 
Carotid  artery,  common,  194 
external,  194 
internal,  194 

gland,  303,  308 
Carpus,  bones  of,  90 
Cartilage,  51,  106 

arytenoid,  236 

chondroblasts  in,  51 

costal,  83 

cricoid,  235 

elastic,  52 

hyaline,  51 

of  larynx,  234 

of  Santorini,  236 

of  Wrisberg,  236 

thyroid,  234 

varieties  of,  51 

white  fibrous,  52 

yellow  fibrous,  52 
Casein,  25,  278,  284 
Caseinogen,  25 
Cavity  or  cavities  of  body,  17,  18 

in   bones,   acetabulum,   93,   97 

dorsal,  17 

glenoid,  of  scapula,  84,  85 

nasal,  72 

oral  or  buccal,  252 

orbital,  71 


464 


INDEX 


Cavity   or    cavities,    pelvic,   94, 
95 
inlet,  95 
outlet,  95 

sigmoid,  of  ulna,  89 

thoracic,  79,  233 

tympanic,  of  ear,  408 

ventral,  18 
Cecum,  269 
Celiac  or  cceliac  axis,  203 

branches  of,  203 
Cell,  31 

bioplasm  of,  31 

bipolar  (nerve),  333 

in  brain,  363 

chromatin  in,  33 

division  of,  32 

function  of,  29,  33 

growth  of,  32 

marrow  (bone),  59 

multipolar  (nerve),  333 

nutrition  of,  32 

properties  of,  33 

protoplasm  of,  31 

reproduction  of,  32 

structure  of,  29 

unipolar  (nerve),  333 
Cellulose,  21 

Centre  or   centres   (nerve),    358, 
359,  364 

hearing  (auditory),  366 

memory,  367 

motor,  364 

respiratory,  248 

sensor,  367 

smell  (olfactory),  366 

speech,  367 

taste  (gustatory),  366 

touch,  391 

vasomotor,  187 

vision,  366 

will,  367 
Centres     (nerve)    in    cerebellum, 
359 

cerebrum,  364 

medulla,  358 

pons,  358 
Centrifugal     nerve     fiber.       See 

Glossary. 
Centripetal.    See  Glossary. 
Cerebellum  (brain),  358 

arteries  of,  197 

falx  of,  355 

function  of,  359 

membranes  of.    See  Brain. 

peduncles  of,  358 

tentorium  of,  355,  358 
Cerebrospinal  system,  331,  354 
portions  of,  331,  354 


Cerebrum  (brain),  359 

areas  of,  364 

arteries  of,  197,  198 

cortex,  359 

falx  of,  355 

functions  of,  364 

lobes  of,  361 

membranes  of,  354,  355 
Cervical  plexus,  380 
Chemic  anatomy,  20 

composition  of  body,  20 

physiology,  20 
Chest,  muscle  of,  143,  144 
Chondroblasts,  51 
Chordae     tendineae    (heart),    178, 

179 
Choroid  of  eye-ball,  400 
Chyle,  287 

absorption  of,  287 
Chyme,  278 

Ciliary  processes  of  eye,  401 
Ciliated  epithelium,  43 
Circle  of  Willis,  198 
Circumduction,  joint  or  muscle, 

114 
Circulation,  174 

arterial,  192 

corporeal,  192 

fetal,  185 

lymphatic,  225 

portal,  215 

pulmonary,  192 

systemic,  192 

venous,  210 
Circulatory  apparatus,  174 

anatomy  and  physiology  of, 
174 
Clavicle,  84 
Clitoris,  417 

Coagulation  of  blood,  222 
Coaptation  of  bones,  111 
Coccygeal  gland,  303,  307 
Coccyx,  79 
Cochlea  of  ear,  412 
Coeliac  or  celiac  axis,  203 
Collar  bone,  84 
Colon,  270 

ascending,  270 

blood-supply  of,  205 

descending,  270 

sigmoid,  270 

transverse,  270 
Colostrum,  295 

corpuscles,  295  V 
Columnse  carneic  (heart),  178, 180 
Columnar  epithelium,  42 
Columns  of  the  spinal  cord,  347 
Common  bile  duct,  300 
Compact  bone,  58 


INDEX 


465 


Complemental     volume     of     air, 

246 
Composition  of  bone,  57 
Compounds   of    body,   inorganic, 
25 
organic,    20 
Conductivity  of  a  cell,  33 

of  a  nerve,  343 
Condyles  of  femur,  98 
of  humerus,  87 
of  mandible.  68 
Conjunctiva,  398 
Connective  tissues,  47 
adipose,  50 
areolar,  50 
bone,  57,  58 
cartilage,  51 
elastic,  48 
fibrous,  48 
functions  of,  47 
%    retiform,  49 
varieties  of,  48 
Contractility  of  arteries,  187 
of  muscle,  121 
of  veins,  189 
Contraction      wave      of      heart 

muscle,  181 
Convoluted     tubules      (kidney) , 

317 
Coracobrachialis  muscle,  149 
Cord  spinal,  345 
umbilical,  185 
Corium  (skin),  323 
Cornea  of  eye-ball,  400 
Coronary  arteries,  194 
sinus,  211 

valve  of,  177 
veins,  211 
Corporeal  arterial  system,  192 
Corpuscles,  blood,  219,  220 
colostrum,  295 
Malpighian   (kidney),   317 
number  of  red,  219 

white,  220 
of  Golgi,  123 
of  Krause,  340 
of  Meissner,  340,  391 
of  Merkel,  340 
of  Paccini,  340,  392 
of  Vater,  392 
red,  219 

function  of,  219 
tactile,  391 
Wagner,  391 
white,  220 

function  of,  221 
varieties,  221 
Corpus  aurantii,  179 
callosum,  359 

80 


Corpus  hemorrhagicum,  426 

luteum,  426 
Corti,  organ  of  (ear),  413 
Cortical  localization  of  function 

(brain),  364 
Costal  cartilages,  83 
Course  of  blood  through  chambers 

of  heart,  180 
part  played  by  valves  during, 

182 
Cranial  nerves,  368 
Cranium,  bones  of,  60 
Cretinism,  304 
Cricoid  cartilage,  235 
Chireus  muscle,  162 
Crystalline  lens  of  eye-ball,  401 

function  of,  404 
Cystic  duct,  300 


Defecation,  282 
Deglutition,  276 
Deltoid  muscle,  147 
Dendrites,  333 

Depressor    anguli    oris     muscle, 
130 
labii  inferioris,  130 
muscle  of  hyoid  bone,  136 
Derma  (skin),  323 
Dextrin,  21 

Dextrose  or  dextroses,  21 
Dialysis.     See  Glossary. 
Diapedesis.     See  Glossary. 
Diaphragm,  81,  140 
action  of,  142 
attachment  of,  140,  141 
openings  in,  80,  81,  142 
Diarthrosis,  110 
Diastole  of  heart,  181 
Digastric  muscle,  136 
Digestion,  275 

accessory  organs  of,  251 
action  of  bile  in,  281 
of  colon  in,  282 
of  gastric  juice  in,  277,  278 
intestinal  juice,  279,  280 
pancreatic  juice,  279 
of  glands  of  stomach  in,  265 
of  saliva,  during,  276 
stomach  wall,  277 
villi  of  intestines  in,  287 
chyme  in,   278 
gastric,  277 
in  infants,  283 
in  mouth,  275,  270 
intestinal,  278 
organs  of,  251,  275 


466 


INDEX 


Digestion, peristaltic  wave  during, 
278 
relation  to  digestion,  278 
Digestive  apparatus,  275 
Digits  of  foot,  104 

of  hand,  92 
Distal  or  dorsal.      See  Glossary. 
Dorsal  artery  of  foot,  208 

cavity  of  body,  17 
Douglas,  pouch  or  cul-de-sac  of, 

272 
Duct    or    ducts,    bile,    299,    300 

common  bile,   300 

cystic,  300 

function  of,  291 

galactophorous,  293 

hepatic,  299 

lactiferous,  293 

nasal,  67 

pancreatic,  301 

of  Bartholin,  258 

of  Rivini,  258 

of  Stenson,  257 

of  Wharton,  258 

of  Wirsung,  301 

thoracic,  231 
Ductless  glands,  303 
Ductus  arteriosus,  185 
atrophy  of,  185 

communicus   choledochus,    300 

venosus,  184 
atrophy  of,  185 
Duodenal  glands,  267 
Duodenum,  265 

length  of,  265 
Dura  mater  of  brain,  354 

of  spinal  cord,  346 
Dyspnoea,    233 


Ear,  bones  of,  410 

divisions  of,  407 

external,  407 

internal,  411 

middle,  408 

tympanum,  408 
Ectoderm,  140 
Edema,  286 
Efferent  nerve  cell,  333 

nerve,  339 

neurone,  333 
Elastic  tissue,  48 
Elasticity  of  arteries,  186 

of  veins,  189 
Elbow  bone,  87 
Elevator  muscles  of  hyoid  bone, 

136 


Elimination    of   waste   products, 
skin,  323 
sweat  glands,  328 
urine,  319,  321 
Embryonic  tissue,  49 
Enarthrosis,  108.    See  Table. 
Endocardium,  175 
Endolymph  (ear),  412 
Endomysium,  119 
Endoneurium,  337 
End-organs,  340,  391 
Endosteum,  58  • 

Endothelial  cells,  46 
Energy,  30 

kinetic,  30 

potential,  30 
Ensiform  process  (bone),  82 
Entoderm,  40 
Enzymes.     See  Glossary. 
Epidermis,  323 
Epigastric  region,  264.      See  Fig. 

102 
Epigastrium,  264.     See  Fig.  102. 
Epiglottis,    236 

function  of,  236 
Epirnysium,     118 
Epineurium,    337 
Epithelial  tissue,  40 
function  of,  40,  41 
locations  of,  40,  41 
varieties  of,  41 
Epithelium,  40 

ciliated,  43 

columnar,  42 

glandular,  45 

goblet,  43 

location  of,  40,  41 

neuroepithelium,  44 

respiratory,  244 

simple,  41 

squamous,  41 

stratified,  41 

transitional,  44 

varieties  of,  41 
Equilibrium,  centre  of,  359 
Erythroblasts  in    bone    marrow, 

59 
Erythrocytes  in  blood,  219 

in  marrow,   59 
Esophagus,  260 

length  of,  261 
Ethmoidal  cells,  66 
Eustachian  tube,  258 
Excretion,  definition  of,  293 
Extension  in  a  joint,  112 
Extensor  muscles.     See  Muscles. 
External  oblique  muscle,  143 

pterygoid  muscle,  132 

rectus  of  eye-ball,  127,  128 


INDEX 


467 


Extremities,  lower,  bones  of,   93 

upper,  84 
Extrinsic  muscles  of  larynx,  238 

of  tongue,    132 
Eye,  appendages  of,  397 

chambers  of,  401 

coats  of,  399,  400 

function  of  retina,  403 

muscles  of,  127,  128,  400 

nerve  of,  370 

refracting  apparatus,  404 

relation   to    accommodation, 
404 
Eye-ball,  capsule  of,  396 
Eyebrows,  muscles  of,  126 
Eyelashes,  398 
Eyelids,  397 

glands  in,  397 

muscles  of,  126 


Face,  bones  of,  66 

Facial  artery,  195.     See  Fig.  76. 

nerve,  375 

vein,  212 
Falciform  ligament  (liver),  297 
Fallopian  tubes,  422 
False  vocal  cords,  237 

pelvis,  94 
Falx  cerebelli,  355 

cerebri,  355 
Fascia,  124 

axillary,  143 

Colles,  147 

composition,  124 

deep  layers  of,  124 
perineal,  147 

function  of,  124 

iliac,  145 

ischiorectal,  147 

lata,  160 

of  abdomen,  142,  143 

of  arm,  149 

of  forearm,  150 

of  neck,  137 

of  shoulder,  147 

of  thigh,  159,  160 

of  thoracic  region,  143 

of  perineum,  146 

palmar,  156 

superficial  layer,  124 
Fats,  22 

action  of  pancreatic  juice  upon, 
280 
*     composition  of,  22 

function  of,  22 

location  of,  22 


Fats,  saponification  of,  23,  280 

soaps  from,  23 
Fatty  tissue,  50 
Fauces,  isthmus  of,  256 

pillars  of,  256 
Feces,  283 
Female   organs   of   reproduction, 

417 
Femoral  artery,  206 

vein,  215 
Femur  (bone),  97 
Fenestra  ovalis  (ear),  411 

"i-otundum  (ear),  409 
Fertilization  of  ovum,  35 
Fetal  circulation,  184 
Fibrin,  25,  218,  222 

function  of.  25,  222 
Fibrinogen,  25,  218,  222 

function   of,  in   coagulation  of 
blood,  222 
Fibrocartilage,  52 

white,  52 

yellow,  52 
Fibrous  tissue,  48 
Fibula  (bone),  102 
Fimbriae  of  Fallopian  tube,  423 
Flexion,  in  a  joint,  112 
Flexor  muscles.     See  Muscles. 
Fontanelles  of  infant  skull,  70,  71 
Food,  absorption  of,  29,  30,  287 

action  of  bile  upon,  281 
gastric  juice,  277,  278 
intestinal  juice,  279,  280 
pancreatic  juice,  279 
saliva,  276 

heat  values  of,  311 

relation  to  body  energy,  29,  30 
Foot,  bones  of,  102 
Foramen  magnum,  60 

of  Monro,  363 

of  ovale,  184 
Forearm,  muscles  of,  151 
Fossa  or  cavity.     See  Cavity. 
P>acture,  green-stick,  of  bone,  57 
Frontal  bone,  61 

lobe  of  cerebrum,  361 

sinus,  62 
Fruit-sugar,  22 


Galactophorous  ducts,  293 
Gall-bladder,  299 

duct  of,  300 
Ganglia,  342 

on  roots  of  spinal  nerve,  342, 
350 


468 


INDEX 


Ganglia,  spinal,  342 
sympathetic,  342 
Gangliated  cord,  342,  383 
Gaseous     exchange     of     carbon 
dioxide    in    lungs,     180 
in  tissue,   180 
of  oxygen  in  lungs,  180 
in  tissues,  180 
Gasserian  ganglion,  371 
Gastric  artery,  203 
digestion,  adults,  277 
enzymes  in,  278 
ferments  in,  278 
infants,  283 
glands,  265 
juice,  278 

action  of,  during  digestion,  277 

pepsin  in,  278 

percentage    of    hydrochloric 

acid  in,  278 
rennin  in,  278 
Gastrocnemius  muscle,  168 
Generative  organs,  female,  417 
Geniohyoid  muscle,  136 
Gigantism,  308 

Ginglymus  joint,  108.    See  Table. 
Gland  or  glands,  45 
alveolar,  45 
Brunner's,  267 
cardiac  of  stomach,  265 
carotid,  303,  308 
ductless,  303 
duodenal,  267 
gastric,  265 
intestinal,  267 
lacrymal,  398 
Lieberktihn,  267 
lymph,  225,  227 
mammary,  293 
parathyroid,  303,  305 
parotid,  257 

function  of,  257,  290 
pituitary,  305,  307 
pyloric,  of  stomach,  265 
salivary,  257 
sebaceous,  325,  326 
secreting,  291,  292 
spleen,  305 
sweat,  327 
thymus,  306 
thyroid,  304 
tubular,  45 
Glenoid  cavity  or  fossa,  84,  85 
Gliding  movement  in  a  joint.  111 
Glisson's  capsule  (liver),  298 
Globulins,  varieties  of,  24 
Glomerulus,  317 

Glossopharyngeal    nerve  (ninth), 
377 


Glottidis  rima  (larynx) ,  237 
Glucose,  21 
Glycogen,  21 

formation  of,  299 
Glycogenic  function  of  liver,  299 
Goblet  cells,  43 
Goitre,  305 

exophthalmic,  305 
Golgi,  organ  of,  123 
Grape-sugar,  21 

Green-stick  fracture  of  bone,  57 
Gristle  of  bone,  23 
Growth  of  a  cell,  32 
Gullet,  260 


Hair  or  hairs,  325 
follicle,  326 
function  of,  325 
location  of,  325 
Hand,  bones  of,  92 
pronation  of,  158 
supination  of,  158 
Haversian  canals  (bone),  58 

system,  59 
Head,  bones  of,  59 
Hearing,     centre     of      (auditory 
area),    366 
nerve  of,  377 
parts  essential  to,  414 
sound  waves,  414,  415 
Heart  (myocardium),  174 

atrioventricular   bundle    (His) , 
181 
function  of,  181 
auricle,  left,  179 

openings  in,  179 
right,  176 

openings  in,  176,  177 
auriculoventricular  groove,  175 
openings,  175,  177 
septum,  175 
beats,  183 
felt  best,  175 
heard  best,  183 
number  of,  per  minute,  183 
regulation  of,  181 
cavities  of,  175 
chordae  tendineae,  178,  179 
contraction  wave  of,  180 

regulation  of,  181 
conus  arteriosus,  178 
coronary  valve,  177 
coverings  of,  174 
columnse  carnese,  178,  180 
diastole  of,  181 
dimensions  of,  175 


INDEX 


469 


Heart,  fetal  circulation  of,  184 
interventricular  groove,  175 

septum,  175 
musculi  pectinati,  178 
openings  into,  176,  179 
within,  175,  177,  178 
papillary  muscles,   179 
position  in  chest,  174,  175 
relation    to    chest    wall,     174, 

175 
sounds,  183 
cause  of,  183 
character  of,  183 
heard  best,  183 
septum  of  ventricles,  175 
sinus  (blood),  211 
systole  of,   181 
valves  of,  179 
coronary,  177 
mitral  or  bicuspid,  179 
semilunar,  178,  179 
tricuspid,  178 
veins  of,  211 
ventricles  of,  left,  179 

right,  178 
weight,  female,  175 
male,  175 
Heat  dissipation,  311,  312 
factors  essential  to,  311 
production,  310 

factors  essential  to,  310 
relation  of  calorie  to,  311 
units,  311 

value  of  food,  311,  312 
Hemoglobin,  219 

relation  to  respiration,  247 
Hepatic  artery,  203 
cells,  298 
ducts,  299 
Hip,  bon'e  of,  97,  98 
His,  bundle  of,  181 
Howship's  fovea,  58 
Human  anatomy,  17 

physiology,  17 
Humerus  (bone),  85 
Hunter's  canal,  163 
Hyaline  cartilage,  51 
Hydrocarbons  (fats),  22 
Hydrochloric     acid      in     gastric 
juice,  278 
percentage  of,  278 
Hymen,  419 
Hyoid  (bone),  68 
Hypochondriac   region,    264 

See  Fig.  102. 
Hypochondrium,  264.      See    Fig. 

102. 
Hypogastric    region,     264.       See 
Fig.   102. 


Hypogastrium,    264,       See    Fig. 

102. 
Hypoglossal  nerve,  379 
Hypophysis.    See  Pituitary  body. 


Ileo-cecal  valve,  269 

Ileum,  265 

Iliac  artery,  205,  206 

veins,  215 
Ilium,  93 

Incus  (bone  of  ear),  410 
Inferior  constrictor  muscle,  133 

vena  cava,  213 
Inguinal     regions     of     abdomen, 

264.     See  Fig.  102. 
Innominate  artery,  194 

vein,  211 
Inorganic    compounds    of    body, 
25 
of  bone,  57 
Insalivation,    275 
Insertion  of  a  muscle,  123 
Intercostal  arteries,  202 
muscles,  140 
spaces,  79 
Internal    oblique    muscle    of    the 
abdomen,  143 
pterygoid  muscle,  132 
rectus  of  eye-ball,  127,  128 
secretion,  290 
definition  of,  290 
organs  of,  290 
Interventricular  septum   (heart), 

175 
Intervertebral  cartilages,  72 

foramen,  75 
Intestinal  digestion,  279 
glands,  267 
invertin  in,   280 
juice,  280 
Intestines,  large,  269 
function  of,  282 
length,  269 
structure  of,  272 
small,  265 

function  of,  279,  280 
structure  of,  265 
Intrinsic  muscles  of  larynx,  238 

of  tongue,    132 
Invertin,  280 

Involuntary  muscle  fiber,  120 
non-striated,    120 
striated,  120 
Iris,  400 
Iron,  26 
Irritability  of  a  cell,  33 


470 


INDEX 


Irritability  of  muscle  tissue,  121 

of  nerve  tissue,  343 
Ischium  (bone),  93 
Island  of  Reil,  361 
Islands  or  areas  of  Langerhans, 

302 
Isthmus  of  fauces,  256 


Jejenum,  265 

Joint  or  joints  (articulation),  106 

amphiarthrosis,  109 

arthrodial,  108.    See  Table. 

ball-and-socket,      108.       See 
Table. 

bones  in,  106 

cartilage  in,  106 

classification     of,      108.        See 
Table. 

condyloid,  108.    See  Table. 

diarthrosis,  110 

hinge,    108.      See    Table. 

immovable,    109 

kinds  of  movement  in,  111 

ligaments  in,  106 

mixed,  109 

movable,  110 

parts  forming,  106 

pivot,  108.    See  Table. 

saddle,  108.    See  Table. 

symphysis,  109 

synarthrosis,  109 
^     syndesmosis,  110 

synovial  membrane  in,  106 

table  of  classification,  108 
Jugular  veins,  212 


Katabolism,  29 
Kidneys,  314 

blood-supply  of,  205 

Bowman's  capsules,  317 

calices  in,  316,  317 

capsule  of,  314 

cortex  of,  314 

dimensions  of,  314 

fixation  of,  314 

glomerulus  in,  317 

loops  of  Henle,  317 

medulla,  316 

structures  of,  316 

papilla  in,  317 

pyramids  of,  317,  318 

relations  of,  314 

secretion  of  urine  by,  319 


Kidneys,  structure  of,  314 

tubules  in,  epithelium  of,  318, 
319 
function  of,  318,  319 
uriniferous,  317 
waste  products  eliminated  by, 
320 
Karyokinesis,  32 
Kinetic  energy,  30 
Krause,  corpuscle  of  (skin),  340 


Labia  majora,  417 

minora,  417 
Labyrinth  of  ear,  411,  412 

membranous,  412 

osseous,  411 
Lacrymal  apparatus,  398 

bones,  67 

ducts,  398 

gland,  398 

sac,  398 
Lactation,  293 
Lacteals,  287 

function  of,  287 

location  of,  287 
Lactiferous  ducts,  293 
Lactose,  22 
Lacunae  of  bones,  58 
Langerhans,  areas  of,  302 
Large  intestines,  269 

divisions  of,  270 
Larynx,  234 

cartilages  of,  234 

interior  of,  237 

ligaments  of,  234 

relation  of,  234 

vocal  cords,  237 
Latissimus  dorsi  muscle,  139 
Leg,  bones  of,  99 

muscles  of,  167 
Leukocytes  in  blood,  220 

in  marrow,  59 

varieties  of,  221 
Levator  anguli  oris  muscle,    129 

labii  superioris  alseque  nasi,  129 
superioris,    129 

menti,  130 

palpebrae  superioris,   127 
Levatores  costarum  muscles,  140 
Levulose,  22 

Lieberkiihn,  glands  of,  267 
Ligaments,  106 

annular,  124.  151 

composition  of,  107 

fimction  of,  106 

of  larynx,  236 

of  liver,  297 


INDEX 


471 


Ligaments  of  uterus,  422 

tarsal,  126,  .397 
Ligamentum  nuchse,  137 
Light,  rays  of,  in  normal  eye,  403 
refractory    apparatus    in    con- 
verging rays  of,  404 
relation  of  retina  to,  403 
Limbs,  lower,  bones  of,  03 

upper,  84 
Line,  ileopectineal,  94 
Linea  alba,  144 
semilunaris,  144 
transversse,  144 
Liver,  295 

blood-supply  of,  203 
dimensions  of,  295 
duct  of,  299 
fissures  of,  297 
functions  of,  299 
glycogen,  formation,  299 
ligaments  of,  297 
lobes  of,  297 
lobules,  298 
portal  vein  of,  216 
secretion  of  bile,  281 
structure  of,  297 
urea  formation  iif,  299 
weight  of,  295 
Lower  extremity,  bones  of,  93 
arteries  of,  206 
muscles  of,  159 
veins  of,  215 
Lower  jaw-bone,  68 
Lumbar  artery,  203 

region  of  abdomen,   264.      See 

Fig.    102. 
vertebra,    72 
Lungs,    241 

air  sacs  in,  244 

alveoli  of,  244 

anatomy  of,  241 

blood-supply  of,  244 

bronchi  in,  243 

bronchioles,  244 

carbon    dioxide    exchan"ge    in, 

180,  244 
lobes  of,  243 
lobiiles  of,  244 

oxygen  exchange  in,    180,   244 
relation  of  pleura  to,  241 
respiratory  epithelium,  244 
root  of,  243 
structure  of,  243 
vital  capacity  of,  246 
volumes  of  air  Ijreathed  during 
respiration,    245 
varieties  of,  245,  246 
Lymph,   absorption  of,  225,  287 
theory  of,  288 


Lymph  capillaries,  225,  226,  287 
blood  capillaries   in   relation 
with,  226,  287 
composition  of,  228 
direction  of  flow,  227,  228 
function  of,  279 
glands  or  nodes,  225,  227 
afferent  vessels  of,  227 
efferent  vessels  of,  227 
function  of,  227 
nodules,  267 

Peyer's  patches,  267,  268 
solitary,  267 
-  spaces,  225,  287 

relation    to    capillaries,    226 
287 
to  digestion,   287 
in    villi   of   small   intestines, 
287 
Lymphatic  ducts,  right,  231 
empties,  231 
parts  drained  by,  231 
system,  225 
thoracic,  231 
empties,  231 
function  of,  231 
relation  of,  231 
vessels,  226 
coats  of,  226 
deep,  226 
function  of,  226 
structure  of,  227 
superficial,  226 
Lymphoid  tissue,  50 


M 

Macula  lutea  (eye-ball) ,  402 
Malar  bone,  68 
Malleolus,  external,  102 

internal,  101 
Malleus  (ossicle  of  ear),  410 
Malpighian  corpuscles  of  kidney 
317 
of  spleen,  306 

layer  of  skin,  323 
Maltose  or  malt-sugar,  22 
Mammary  glands,  293 
Mandible  (bone),  68 
Maple-sugar,  22 
Marrow  of  bone,  59 

cavity,  59 

cells,  59 
Masseter  muscle,  132 
Mastication,  275 

muscles  of,  132 
Mastoid  cells  (ear),  64 


472 


INDEX 


Maturation  (ovum),  35 
Maxilla  (bone),  67 
Meatus,  external  auditory,  65 
Mediastinum,   241 
Medulla  (oblongata),  355 
centres  in,  357 
functions  of,  357 
of  kidney,  316 
Medullary    canal    of     bone,    55, 
59 
endosteum  of,  58 
rays  of  kidney,  317 
Medullated  nerve  fiber,  334 
Meibomian  glands,  397 
Meissner  corpuscles,  340 
Membrana    granulosa   of   ovary, 
424 
tympani,  408 
Membrane  or  membranes,  45,  291 
of  brain,  355 
mucous,  45,  291 
function  of,  45,  291 
location  of,  45 
structure  of,  45 
serous,  46,  291 

function  of,  46,  47 
location  of,  46 
of  spinal  cord,  346 
synovial,  107,  292 
function  of,  107,  292 
location,  107 
varieties  of,  107 
Memory,  centre  of,  367 
Menopause,  428 
Menses,  427 
Menstruation,  427 
cause  of,  427 
period  of,  427 
Mesenteric  artery,  inferior,  205 
superior,  205 
vein,  inferior,  216 
superior,  216 
Mesoderm,  40 
Metabolism,  29 
Metacarpal  bones,  92 
Metatarsal  bones,  104 
Micturition,  314 
Middle  constrictor  muscle,  133 
Milk,  291 

action  of  rennin  upon,  279 
amount    secreted    in    twenty- 
four  hours,  294 
colostrum  of,  295 
difference    in    composition    of, 
cow,  294 
human.  294 
as  a  food,  294 
Milk-sugar  or  lactose,  22 
Mineral  salts  in  bone,  57 


Molasses,  22 

Molecular  disturbance  of  a  nerve, 

344 
Mons  veneris,  417 
Motility  of  a  cell,  33 
of  white  cells,  220 
Motor  areas  in  brain,  364 
nerve,  339 

roots  of  spinal  cord,  349 
Mouth  or  oral  cavity,  252 

digestion  in,  275,  276 
Movements,  kinds  of,  in  a  joint, 

111 
Mucin,  45,  291 
Mucous  membranes,  45,  291 
function  of,  45 
layers  of,  45 
location  of,  45 
secretions,  291 
varieties  of,  291 
Multipolar  nerve  cell,  333 
Muscle  or  muscle  tissue,  117 
abductor  hallucis,  171 

minimi  digiti,   of  hand,   157 

of  foot,  171 
pollicis,  157 
adductor  brevis  (thigh),  166 
longus  (thigh),  164 
magnus  (thigh),  166 
obliquus  hallucis,  171 

pollicis,  157 
transversus   hallucis,    171 
pollicis,  157 
anconeus,  155 
arrangement  of  muscle  fibers, 

118,  119 
attachment  of,  to  skeleton,  122 
biceps,  arm,  149 

leg,  164 
brachialis  anticus,  149 
buccinator,  131 
classification  of,  117 
constrictor,  of  pharynx,  133 
contractility  of,  121 
coracobrachialis,  149 
cranial,  124 
crureus,  162 
deltoid,  147 
depressor  anguli  oris,  130 

labii  inferioris,    130 
depressors  of  hyoid  bone,  136 
derivation  of  names,  122 
diaphragm,  140 
digastric,  136 

elevators   of   hyoid    bone,    136 
extensor  brevis  digitorum,  170 
pollicis,  156 
carpi  radalis  brevior,  154 
longior,  154 


INDEX 


473 


Muscle  or  muscle  tissue,  extensor 
communis  digitorum,  154 
indicis,    156 
longus  digitorum,  167 
hallucis,  167 
pollicis,  156 
minimi  digiti,  155 
ossis  metacarpi  pollicis,   156 
external  obliqueof  abdomen, 146 
pterygoid,  132 
rectus  of  eye-ball,  127,  128 
flexor  accessorius,  171 
brevis  digitorum,   170 
hallucis,  171 
minimi  digiti,  157 
pollicis,  157 
carpi  radialis,  151 

ulnaris,  152 
longus  digitorum,  169 
hallucis,  170 
pollicis,  153 
profundus  digitorum,  153 
sublimus  digitorum,  152 
gastrocnemius,  168 
geniohyoid,  136 
gluteus  maximus,  160 
medius,  160 
minimus,  160 
gracilis,  166 
iliacus,  145 
inferior  constrictor,  133 

rectus  of  eye-ball,  127,  128 
infracostales,  140 
infraspinatus,  148 
insertion  of,  123 
intercostal,  140 
internal  pterygoid,  132 
oblique,  142 
rectus,  127,  128 
interossei  of  foot,  172 

of  hand,  157,  158 
involuntary   non-striated,   117, 
120 
striated,  117,  120 
latissimus  dorsi,  139 
levator  anguli  oris,  129 

labii  superioris  alaeque  nasi, 
129 
superioris,  129 
menti,  130 

palpebrae  superioris,  127 
levatores  costarum,  140 
lumbricales  of  hand,  158 
masseter,  132 
middle  constrictor,  133 
motor  plate,  nerve  ending,  339 
mylohyoid,  136 
nerve  endings  in,  339 
occipitofrontalis,  125 


Muscle  or  muscle  tissue  of  abdo- 
men, 142,  145 
of  back  and  neck,  137 
of  cheek,  130 
of  chest,  144 
of  external  ear,  125 
of  eye-ball,  127,  128 
of  eye-brows,  126 
of  eye-lids,  126 
of  fingers,  152,  153 
of  foot,  170 
of  forearm,  151 
of  hand,  157,  158 
"    of  head  and  neck,  124,  134,  136 
of  hypothenar  eminence,  157 
of  larynx,  238 
of  little  finger,  157 

toe,  171 
of  lower  extremity,  159 

of  upper,  147 
of  mastication,  132 
of  mouth,  130 
of  nose,  129 
of  orbits,  127,  128 
of  palate,  133 
of  pharynx,  133 
of  shoulder,  147,  148 
of  thenar  eminence,  157 
of  thigh,  161 
of    thoracic    (anterior)    region, 

143 
of  thorax,  139 
of  tongue,  132 
of  trunk,  137 
omohyoid,  136 
opponens  minimi  digiti,  157 

pollicis,  157 
orbicularis  oris,  130 

palpebrarum,  126 
origin  of,  122,123 
palmaris  brevis,  157 

longus,  151 
pectineus,  164 
pectoralis  major,  144 

minor,  144 
peroneus  brevis,  168 

longus,  168 
plantaris,  169 
platysma,  135 
popliteus,  169 
pronator  quadratus,  153 

radii  teres,  151 
pyramidalis,  143 
quadratus  lumborum,  145 
quadriceps  extensor  tendon,  162 
recti  of  eye-ball,  128 
rectus  of  abdomen,  143 
relation  of  aponeurosis  to,  123 

of  fascia  to,  124 


474 


INDEX 


Muscle  or  muscle  tissue,  relation 

of  nerve  to,  339 
risorius,    132 
sarcolemma   of   muscle    tissue, 

117 
sarcoplasm,    117 
sartorius,    162 
semimembranosus,  164 
semitendinosus,  164 
soleus,  168 
sternomastoid,  136 
stimuli,  122 

striated,       involuntary,       117, 
120 

voluntary,    117 
stylohyoid,  136 
stylopharyngeus,  133 
subclavius,  144 
subscapular,  148 
superior  constrictor,  133 

oblique  of  eye-ball,  129 

rectus,  127 
supinator  brcvis,  155 

longus,  154 
supraspinatus,  148 
temporal,  132 
tendons  of,  122,  123 
tensor  fascia  femoris,  162 

tarsi,  126 
teres  major,  148 

minor,  148 
tibialis  anticus,  167 

posticus,  170 
tissue,  117 

classification  of,  117 

endomysium  of,  119 

epimysium  of,  118 

perimysium  of,  119 

physiological    properties    of, 
121 
transversalis  of  abdomen,    143 
trapezius,  137 
triangularis  sterni,  140 
triceps,  150 
vastus  externus,  162 

internus,  162 
voluntary,  117 
Muscularis  mucosae,  45 

importance   to   contraction    of 

arteries,  187 
Myelin    sheath    of    nerve    fiber, 

335 
Mylohyoid  muscle,  136 
Myocardium      (heart      muscle) , 

175 
Myology,  definition  of,  18,  117 
Myosin  of  muscle  tissue,  25 
Myosinogen,   25 
Myxedema,  304 


N 


Nails,  finger  and  toe,  325 
Nasal  bones,  66 

cavities  or  fossae,  72,  395 

function  of,   in    respiration, 
233 
duct,  67,  395,  398 
septum  or  wall,  66,  67,  72 
Nares,  anterior,  72 

posterior,  72 
Nerve  or  nerves,  335 
abducens,  375 
axis-cylinder  or  axone,  335 
afferent,   340 
anatomy     and     physiology     of 

nerve  system,  331 
auditory  (eighth),  377 
bloodvessels  of,  335 
cell,  331 

classification    of,    in    spinal 
cord,  349 

size  of,  333 

structure  of,  333 
central  system,  345 
cerebrospinal  system,  331 

classification  of,  342 
connective  -  tissue      trabeculae, 

337 
cranial,  368 
efferent,  339 
eighth  cranial,  377 
endings  of,  339,  340 
endoneurium  of,  337 
epineurium  of,  337 
eleventh  cranial,  378 
facial  (seventh),  375 
fiber,  334 

amyelinic,  334,  335 

medullated,  334 
myelin  of,  335 
nodes  of  Ranvier  on,  335 
substance  of  Schwann,  335 

myelinic,    334 

non-medullated,  334,  335 
fifth  cranial,  371 
first,  368 
fourth,  371 
function  of,  336 
ganglia,  ganglion,  342 

sympathetic,  342 
glossopharyngeal   (ninth),  377 
gangliated  cord,  383 

nerves,  385 

function  of,  386 

relation    of    rami    communi- 
cantes  to,  385 

structure  of,  383 
hypoglossal  (twelfth),  379 


INDEX 


475 


Nerve    or   nerves,   inferior    max- 
illary division  of  fifth,  374' 
impulse,  343 

direction  of  afferent,  344 
efferent,  344 
motor,  344 
of  sensor,  344 
lingual,  374 

molecular,  disturbance  in,  344 
neurilemma  of,  335 
neuroglia  of,  337 
ninth  cranial,  377 
oculomotor  (third),  370 
olfactory  (first),  368 
ophthalmic    division    of    fifth. 

373 
optic  (second),  370 

chiasm,  370 

tract,  370 
origin  of,  338 
pars  intermedia,  375 
perineurium  of,  337 
physiology  of,  343 
plexus,  340 

pneumogastric  (tenth),  378 
reflex  action  of,  292 
second  cranial,  370 

seventh,  376 

sixth,  375 
secretor,  328 

regulation  of  blood  pressure, 
328 
seventh  cranial,  375 
spinal,  346,  379 

accessory,  eleventh,  378 

cells,  349 

afferent,  349 
classification  of,  349 
efferent,   349 
intrinsic,  349 

ganglia  on,  342 

names  of,  349 

number  of,  349 

rami  communicantes,-385 
stimuli,  343 

structure     of     nerve     svstem, 
331 
cell,  333 

of  neurone,  333 

supporting,  337 
superior   maxillary   division   of 

fifth,  373 
sympathetic  system,  383 

function  of,  383 

ganglia  in,  383 
tenth  cranial,  378 
tonus  of  a  nerve,  352 
trochlea  (fourth),  371 
vasomotor,  187,  328 


Nerve  or  nerves,    vasomotor  to 
bloodvessels,  187 

vasoconstrictor,  187 

vasodilator,  187 
Neuroepithelial  cells,  44 
Neurone  or  nerve  cell,  331 

afferent  (sensor),  333 

axis-cylinder  or  axone  of,  333 

bipolar,  333 

dendrites  of,  333 

efferent,  333 

motor,  333 

excitoglandular,  333 
excitomotor,  333 

multipolar,  333 

sensor,  333 

structure  of,  333 

unipolar,  333 
Neuroglia,  337 
Neurology,  definition  of,    18 
Neutral  fats,  23 
Non-medullated  nerves,  334,  335 
Nose,  bones  of,  66 

muscles  of,  129 

openings  of,  72 
Nucleolus  of  a  cell,  32 
Nucleus  of  a  cell,  32 
Nutrition  of  a  cell,  32 
Number  of  bones  in  body,  54 


Oblique     muscles     of     eye-ball, 

127,  128 
Occipital  bone,  60 

lobe  of  cerebrum,  361 
Occipitofrontalis  muscle,  125 
Oculomotor  (third)  nerve,  370 
Odors,  relation  of  sense  of  smell, 

396 
Olecranon  fossa,  87 

process,  87 
Olein,  23 
Olfactorv  area,  366 

bulb,  369 

filaments,  369 

nerve,  368 

tract,  370 
Omentum.    See  Glossary. 
Ophthalmic  division  of  fifth  nerve, 

373 
Optic  chiasm,  370 

nerve,  370 

tract,  370 
Orbicularis  oris  muscle,  130 

palpebrarum,  126 
Orbital  cavities,  71 
boundaries  of,  71 


476 


INDEX 


Orbital  cavities,  contents  of,  396 

Orbits,  71 

Organ  of  Corti  (ear),  413 

of  Golgi,  123 
Organic  acids,  27 

compounds,  20 
Organs  of  digestion,  251 

of  reproduction,  417 

of  respiration,  233 

of  voice,  234 
Origin  of  a  muscle,  123 

of  a  nerve,  338 
Osmosis.    See  Glossary. 

of  lymph,  225 
Ossicles  (bones  of  ear),  410 
Ossification.    See  Glossary. 
Osteoblasts,  57 
Osteoclasts,  58 
Osteology,  definition  of,  18 
Otoliths,  413 
Ovarian  artery,  205 
Ovaries,  423 

blood-supply  of,  205 

ligaments  of,  423 
Ovulation,  425 
Ovum,  35,  424 

development  of,  424 

fertilization  of,  35,  425,  426 

maturation  of,  35 
Oxidation  of  blood,  220 

of  tissue,  220 
Oxyhemoglobin,  220 


Pain,  sense  of,  393 
Palate,  arches  of,  256 

glands  of,  256 

hard,  256 

pillars  of,  256 

soft,  133,  256 
Palate  bone,  68 
Palmar  arches,  deep,  198,  201 
superficial,  198,  201 

fascia,  156 
Palmaris  brevis  muscle,   157 

longus,  151 
Palmitin,  23 
Pancreas,  301 

blood-supply  of,  203 

dimensions  of,  301    • 

function  of,  279,  302 

islands  of  Langerhans  in,   302 

structure  of,  302 
Pancreatic  juice,  279 

action  of,  upon  food,  279 

amylopsin  in,  280 

in  intestinal  digestion,  279 


Pancreatic  juice,  steapsin  in,  280 

trypsin  in,  280 
Papilla?  of  skin,  324 
Papillary  muscles  in  heart,    179 
Parathyroids,  303,  305 

function  of,  305 
Parietal  bones,  60 
Parotid  gland,  257 

duct  of,  257 
Patella  bone,  knee-cap,  99 
Pectoralis  major  muscle,  144 

minor,  144 
Pelvic  cavity,  93 

boundaries  of,  93 
Pelvis  as  a  whole,  93 

false,  94 

inlet,  95 

outlet,  95 

true,  95 
Pepsin,  278,  279 

action  of,  in  gastric  digestion, 
279 
Peptones,  25,  278,  279 
Pericardium,  174 

fibrous  layer,  174 

serous,  174 
Perichondrium,  51 
Perilymph  (ear),  412 
Perimysium,  119 
Perineum,  fascia  of,  146 

muscles  of,  146 
Perineurium,  337 
Periosteum,  57 
Peripheral  resistance,  191 
Peristalsis,  278 

relation  of,  to  digestion,  278 
Peroneus  brevis  muscle,  168 

longus,  168 
Perspiration,  327 

function  of,  328 

glandular  activity,  328 
nerves  controlling,  328 
blood-pressure,  328 
Perspiratory  apparatus,  19 
Peyer's  patches,  267,  268 
Phagocytes,  221 
Phagocytosis,  221 
Phalanges  of  foot,  104 

of  hand,  92 
Pharynx,  258 

boundaries  of,  258 

length  of,  259 

muscles  of,  132 

structure  of,  258 
Phonation,  238 
Phosphorus  in  body,  26 
Physiological  properties  of  muscle 

tissue,  121 
Physiology,  definition  of,  17 


INDEX 


477 


Pia  mater  of  brain,  355 

of  spinal  cord,  346 
Pigmented  cell,  44 
Pituitary  body,  307 

function  of,  307 
Place,  sense,  skin,  393 
Placenta  (after-birth),  184 
Plantaris  muscle,  169 
Plasma  of  blood,  217 
Platysma  muscle,  135 
Pleura,  240 

prevent  friction  during  respira- 
ation,    242 

structure  of,   240 
Pleural  cavity,  240 
Plexus  of  nerves,  340 

brachial,  380 

cervical,  380 

lumbar,  382 

sacral,  382 

venous,  211 
Pneumogastric  (tenth)  nerve,  378 
Pons  varolii.  357 

function  of,  357 

structure  of,  357 
Popliteal  artery,  208 

vein,  215 
Popliteus  muscle,  169 
Portal  circulation,  215 

system,  215 

vein,  215 
Potential  energy,  30 
Pressure,   blood.     See  Blood-    ' 
pressure. 

sense  (skin),  393 
Prickle  cells,   43 
Principles,  proximate,  20 
Pronation,  158 
Pronator  quadratus  muscle,   153 

radii  teres,  151 
Proteins  or  proteids,  23 

composition  of,  23 
Proteoses,  25,  279 
Protoplasm,  31 

composition  of,  32 

of  ovum,  32 

properties  of,  32,  33 
Proximate  principles,  20 
Psoas  magnus  muscle,  146 

parvus,  146 
Ptyalin,  276 
Pulmonary   arterial   system,    192 

artery,  178,  192 

circulation,  192 

vein,  178 
Pulse,  189 

cause  of,  190 

number  of   beats   per  minute, 
190 


Pulse,  physiology  of,  190 

varieties  of,  190 

where  to  count,  189 
Pupil  of  eye,  400 
Pyloric  valve  of  stomach,  263 
Pylorus  of  stomach,  263 


Quadriceps  extensor  tendon,  162 


Radial  artery,  198 

vein,  213 
Radius,  89 

Rami  communicantes,  385,  386 
Ranvier,  nodes  of,  335 
Reaction,  chemical.  See  Glossary. 
Receptaculum  chyli,  231 
Recti   muscles   of   eye-ball,    127, 

128 
Rectovaginal  pouch,  272 
Rectum,  272 
Rectus  femoris  muscle,  162 

muscle  of  abdomen,  143 
Red  cells  or  corpuscles,  217,  219 
Reflex  action,  352 

in  gland  secretion,  292 
Regions  of  abdomen,  264.      Fig. 

102 
Renal  arteries,  205 
Rennin,    278 

action  of,  in  gastric  digestion, 
adult,   279 
infant,    284 
upon  milk,  279 
Reproduction  of  a  cell,  32 

organs  of,  female,  417 
Reserve   volume   of   air    (lungs), 

246 
Residual  volume  of  air   (lungs), 

246 
Resistance      peripheral       (blood 

pressure),  191 
Respiration,  233,  245 

carbon  dioxide  given  off  during, 
244 

cause  of,  249 

changes  of  composition  of  air 
during,  246 

frequency  of,  245 

function  of,  245 

nasal  cavities,  relation  to,  233 

organs  of,  233 

oxygen    absorbed    during,    244 

rate  of,  245 


478 


INDEX 


Respiration,    complemental     air, 
246 

relation  of  nerves  to,  248 

reserve,  246 

residual,  246 

respiratory  epithelium  in,  244 

tidal,  245 

vital  capacity  of  lungs  in,  246 

volumes  of  air  breathed  during, 
245 
Respiratory  apparatus,  19,  233 

centre  (nerves),  248 

epithelium,  244 
Retiform  tissue,  49 
Retina  (eye-ball),  401 

function  of,  403 

layers  of  cells  in,  403 

macula  lutea  in,  402 

rods  and  cones  in,  403 
function  of,  403 
Ribs,  false  or  asternal,  82 

floating,  82 

peculiar,  83 

true  or  sternal,  82 

typical,  82 
Risorius  muscle,  132 
Rotation   of   a   joint   or   muscle, 

115 
Ruga?  of  bladder,  318 

of  stomach,  264 

of  vagina,  420 


Saccharoses,  21,  22 
Saccule  of  larynx,  237 

of  membranous  labyrinth,  412 
Saliva,  275,  291 

chemical  action  of,  276 

physical  action  of,  276 
Salivary  glands,  257 
Salt  or  sodium  chloride  in  body, 

26 
Salts,  mineral,  in  body,  26 

in  bone,  57 
Saphenous  vein,  long,  215 

short,  215 
Saponification,  23 
Sarcolemma  (muscle  tissue),  117, 

118 
Sarcoplasm  (muscle    tissue),   117 

178 
Sartorius  muscle,  162 
Scalp,  layers  of,  124,  125 
Scapula  (bone),  84 
Scarpa's  triangle,  206 
Schwann,     white     substance     or 

sheath  of,  335 


Schwann,    sclerotic  coat  of   eye- 
ball, 399 
Sebaceous  glands,  325,  326 
Sebum,  327 
Secreting  glands,  292 
Secretions,  290 
external,  290 

classifications  of,  291 
gastric  juice,  291 
milk,  291 
mixed,  46 
mucous,  46,  291 
saliva,  29 
serous,  46,  291 
synovial,  292 
tears,  398,  399 
internal,  290,  303 
organs  of,  303 
Secreting  organs,  glands,  291 

membranes,  291 
Secretory  apparatus,  19 
Semicircular  canals  (ear),  411 
Semilunar  valves  (heart),  178,  179 
Semimembranosus  muscle,  164 
Semitendinosus  muscle,  164 
Sensations  in  end-organs  of  skin, 

391 
Sense,  muscle,  394 
of  equilibrium,  359 
of  hearing,  407 
of  sight,  396 
of  smell,  394 
of  taste,  390,  406 
of  touch,  391 

muscle  sense,  394 
place  sense,  393 
pressure  sense,  393 
temperature  sense,  393 
tactile,  390,  391 
Sensor  area  in  brain,  366 
nerve  cell,  333,  349 

fiber,  340 
roots  of  spinal  cord,  350 
Serous  membranes,  46,  291 
function  of,  46,  47,  291 
location  of,  46,  47 
secretions,  291 
Serum  of  blood,  218 
Serum-albumen  in  blood,  24 
Sharpey's  fibers  (bone),  58 
Shin  bone  (tibia),  99 
Shoulder,  muscles  of,  147,  148 
Shoulder-blade,  84 
Sight,  nerve  of,  370,  397 
organs  of,  396 
physiology  of,  403,  404 
sense  of,  396 
Sinus  or  sinuses,  antrum  of  High- 
more,  68,  72 


INDEX 


479 


Sinus  or  sinuses,    coronary    (ven- 
ous), 179,  211 
frontal,  62 
maxillary,  72 
Valsalva,  179 
venous,  of  skull.  211 
Skin.  322 

appendages  of,  325 
derma  of,  322 
end-organs  in,  340 
epidermis  of,  322 
function  of,  323 
layers  of,  epidermis,  323 

dermis,  323,  324 
secretions  from,  323 
sweat  glands  in,  327 
total  area  of,  323 
waste   materials   eliminated 
from,  323 
Skull  as  a  whole,  69 
bones  of  vertex,  71 
fetal,  69 

fontanelles  in,  69,  70 
ossification  of,  69 
venous  sinuses  of,  211 
Small  intestine.      See  Intestines. 
Smell,  nerve  of.  368,  394 
sense  of,  394 
organs  of,  394 
Soaps,  23 
Soleus  muscle,  168 
Sound  waves,  41.5 
cause  of.  415 
Sounds  of  heart.  182 

cause  of.  183 
Speech,  articulate,  238 

centre  of,  367 
Spermatozoon,  35,  425 
Sphenoid  bone,  65 
Spinal  accessory  nerve,  378 
canal,  74,  346 
column,  72 

length  of,  74 
cord,  345 

columns  of,  347 
function  of,  351 
horns  of,  348 
length  of.  347 
membranes  of,  346 
nerve  cells  in,  349 
nerves  of,  349 

number  of,  349 
roots  of.  350,  351 

ganglion  in,  342,  350 
structure  of,  348 
Spinal  nerves,  349 
names  of,  349 
nun\ber  of  pairs,  349 
Splanchnology,  definition  of,  19 


Spleen,  305 

blood-supply  of,  203 

dimensions  of,  305 

function  of,  306 

ligaments  of,  306 

location  of,  305 
Squamous  epithelium.  40 
Stapes  (ossicle  of  ear),  410 
Starch,  21 

action  of  saliva  upon.  276 
pancreatic  juice,  280 
ptyalin,  276 
Steapsin,  280 
*    action   of  intestinal   digestion, 

280 
Stearin,  23 

Sternohyoid  muscle.  136 
Sternomastoid  muscle,  136 
Sternothyroid  muscle.  136 
Sternum  (bone),  82 
Stimuli  of  muscle  tissue,  122 

of  nerves,  343 

relation    of    molecular   distur- 
bance to,   344 
Stomach,  262 

blood-supply  of,  203 

capacity  of  adult's,  263 
of  infant's,  283 

coats  of.  263 

digestion  in,  277 

glands  of,  265 

location  of,  262 

parts  of.  236 

structure  of,  263 
Stomata,  47 

Stratified  epithelium,  41 
Styloglossus  muscle,  132 
Stylohyoid  muscle,  136 
Subclavian  artery,  196 

vein,  212 
Subclavius  muscle,  144 
Subcostal  muscle,  140 
Subcrureus  muscle,  163 
Subcutaneous  tissues,  324 
Sublingual  gland,  257 
Submaxillary  gland.  257 
Sugars  in  body,  21,  22 

dextroses,  21 

saccharoses,  22 
Sulphur  in  body.  26 
Superior  constrictor  muscle.   133 

maxillary      division      of      fifth 
nerve.  373 

rectus  muscle,  127,  128 

vena  cava,  211 
Supination  of  hand.  158 
Supinator     brevis     muscle,      155 

longus,  154 
Suprarenal  glands,  307 


480 


INDEX 


Suprarenal    glands,    function    of, 
307 

location  of,  307 
Swallowing  (deglutition) ,  276 
Sweat,  328.     See  Perspiration. 
Sympathetic  ganglia,  383 

function  of,  386,  387 

structure  of,  383,  387 

system  of,  383 
function  of,  386 
gangliated  cord  of,  385 
Symphysis  pubes,  93 
Synarthrosis  (joint),  109 
Syndesmology,  definition  of,  18 
Syndesmosis,  110 
Synovia,  107 

Synovial  membranes,  107,  292 
Systole  of  heart,  181 


Tactile  cells,  391 

end-organs,  391,  392 
Tarsal  cartilage,  397 

ligaments,  126,  397 
Tarsus,  bones  of,  102 
Taste-buds  (tongue),  406 

end-organs,  406 

nerves  of,  374,  377 

organs  of,  406 

sensations  of,  406 

sense  of,  406 
Tears,  composition  of,  399 

drainage  of,  399 

secretion  of,  398,  399 
Teeth,  252 

appearance  of,  in  infants,  254 

permanent,  253 

structure  of,  253 

temporary,  252 
Temperature  of  body,  312 

at  different  ages,  313 

determination  of,  312 

normal,  adult,  313 
by  axilla,  313 
by  mouth,  313 
by  rectum,  313 
by  vagina,  313 
Temporal  bone,   62 

lobe  of  brain,  361 
Tendo  Achilles,  169 

oculi,  126 
Tenon,  capsule  of,  396 
Tendons,  122 

attachments  of,  123 

composition  of,  123 

function  of,  123 

organs  of  Golgi  in,  123 


Tension,  arterial,  190 

muscle,  121 
Tetany,  305 

Thigh,  muscles  of,  97,  98 
Thoracic  aorta,  202 
branches  of,  202 

cavity,  79 

contents  of,  81 
dimensions  of,  79 

ducts,  231 

functions  of,  231 

relation      of      receptaculum 

chyli  to,  231 
right,  231 
Thorax  as  a  whole,  79 

bones  of,  79 

contents  of,  81 

muscles  of,  139 

openings,  lower,  81 
upper,  79 
Thymus  gland,  306 
Thyroid  cartilage,  234 

gland,  304 

isthmus  of,  304 
Tibia  (bone),  99 
Tibial  artery,  anterior,  208 
posterior,  208 

veins,  215 
Tibialis  anticus  muscle,  167 

posticus  muscle,  170 
Tidal  air,  volume  breathed,  245 
Tissue  or  tissues,  35 

adipose,  50 

areolar,  50 

bone,  57,  58 

cartilage,  51 

classification  of,  40 

connective,  47 

embryonic,  49 

endothelial,  46 

epithelial,  40,  41 

fibrous,  48 

lymphoid,  50 

mucous,  49 

muscle,  117 

neuroepithelial,  44 

origin  of,  35 

osseous  (bone),  57,  58 

retiform,  49 

subcutaneous,  324 
Tone  or  tonus  of  arteries,  190 

of  muscle,  121 

of  nerve,  352 
Tongue,  254 

arteries  of,  255 

muscles  of,  extrinsic,  254 
intrinsic,  254 

nerves  of,  374,  377 

structure  of,  254 


INDEX 


481 


Tongue,  taste  sensations  in,  406, 
407 

touch  sensations  in,  406,  407 

veins  of,  255 
Tonsils,  256 

location  of,  256 
Tonus  of  a  muscle,  121 

of  a  nerve,  352 
Touch,  sense  of,  391 

varieties  of,  392,  393 
Trachea  (windpipe),  238 

dimensions  of,  239 

structure  of,  238,  239 
Transitional  epithelium,  44 
Transversalis  muscle  of  abdomen, 

143 
Transverse  lines  of  abdomen,  144 
Trapezius  muscle,  137 
Triangularis  sterni  muscle,  140 
Triceps  muscle,  150 
Tricuspid  valve  (heart),  178 
Trifacial  or  trigeminal  nerve,  371 
Trigone  of  bladder,  319 
Trochlear  nerve,  371 
True  pelvis,  95 
Trypsin,  279 

action  of,  in  intestinal  digestion, 
279 
Tunica  propria  of    a  membrane, 

45 
Tunics  or  coats  of  arteries,  186 

of  eye-ball,  399 

of  veins,  188 
Turbinated  bones,  68 
Tympanic  cavity  or  tympanum, 
408 
ossicles  in,  410 


Ulna  (bone),  87 
Ulnar  artery,  199 

vein,  213 
Umbilical  cord,  185 

region  of  abdomen,  264.      Fig. 
102 

vein,  184 
Unipolar  neurone    or   nerve  cell, 

333 
Upper  extremity,  arteries  of,  198 
bones  of,  84 
veins  of,  212 
Urea,  322 

production  of,  in  liver,  299 

relation  of,  to  protein  diet,  322 
Ureters,    318 
Urethra,  opening  in  bladder,  319 

function  of,  314 


Urinary  apparatus,  19,  314 
bladder,  318 
capacity  of,  318 
dimensions  of,  318 
function  of,  318 
structure  of,  319 
Urine,  amount  of,  in  twenty-four 
hours,  322 
color  of,  321 
composition  of,  322 
excretion  of,  319 
formation  of,  319 
method  of  secretion,  319 
Uriniferous  tubules  (kidney),  317 

function  of,  318,  319 
Uterine  artery,  206 
Uterus  (womb),  420 
blood-supply  of,  206 
function  of,  422 
parts  of,  420 
structure  of,  421 
Utricle  of  membranous  labyrinth, 

412 
Uvula,  256 


Vagina,  419 

Valsalva,  sinus  of,  179 

Valve  or  valves,  ilecocecal,  269 

of  heart,  coronary,  177 
mitral,  179 
semilunar,  178,  179 
Thebesius,  177 
tricuspid,  178 

of  veins,  189 
Valvulae  conniventes  (intestines), 

266 
Vasa  vasorum  (arteries),  187 
Vasoconstrictor  nerves,  187 
Vasodilator  nerves,  187 
Vasomotor  centre,  187 

nerves,  187,  328 
Vastus  externus  muscle,  162 

internus  muscle,  162 
Vater,  ampulla  of,  302 
Vein  or  veins,  189 

axillary,  213 

basilic,  213 
median,  213 

blood-pressure  in,  191 

cardiac,  211 

cava,  vena,  inferior,  213 
superior,  211 

cephalic,  213 

coats  of,  188 

contractility  of,  189 

coronary,  211 


482 


INDEX 


Vein   or  veins,    deep,    210,    211, 

215 
description  of,  210 
elasticity  of,  189 
facial,  212 
femoral,  215 
function  of,  185,  189 
of  heart,  211 
iliac,  common,  215 

left,  215 

right,  215 
innominate,  211 
jugular,  external,  211 

internal,  211 
mesenteric,  inferior,  216 

superior,  216 
peroneal,  215 
plexus,  venous,  211 
popliteal,  215 
portal,  215 

system  of,  215 

tributaries  of,  216 

veins  forming,  216 
pulmonary,  179,  180 
pyloric,  216 
radial,  213 
saphenous,  long,  215 

short,  215 
sinus,  coronary,  211 

venous,  211 
structure  of,  185 
subclavian,  213 
superficial,  210,  212,  215 
systemic,  210 
temporal,  212 
temporomaxillary,  212 
tibial,  215 
ulnar,  213 

upper  extremity,  212 
valves  of,  189 
Vena  cava,  inferior,  213 

superior,  211 

comites,  211,  215 

Venous  circulation,  189 

pressure  of  blood  in,  191 
Ventral  cavity  of  body,  18 
Ventricles  of  brain,  362 
of  heart,  178,  179 
of  larynx,  237 
Venules,  189 

function  of,  189 
Vermiform  appendix,  269 
Vernix  caseosa  (newborn),  327 
Vertebra  or  vertebrae,  76 
description  of,  75 
names  of  divisions  of,  72 
number  of,  72 
Vertebral  column  as  a  whole,  72 
bones  of,  72 


Vertebral,  curvatures  in,  73 

length  of,  74 
Vertex  of  skull,  bones  of,  71 
Vesicle,  blastodermic,  40 
Vestibule  of  internal  ear,  411 

of  vagina,  419 
Vibrations,  414 

effect  upon  ear-drum,  414 

relation    to    hearing,    414,    415 
Villi,  function  of,  in  relation    to 
absorption,  287 

relation  to  digestion,  287 

of  small  intestines,  287 

structure,  287 
Vision,  parts  of  eye-ball  concerned 
with,  403,  404 

refracting  apparatus  in,  404 
Vital  capacity  of  lungs,  246 
Vitelline  membrane,  35 
Vitellus,  35,  420 
Vitreous  humor  (eye-ball),  401 
Vocal  cords,  false,  237 

true,  238 
Voice,  production  of,  238 

vocal  sounds  in,  238 
Volumes  of  air  breathed  during 
respiration,  245 

complemental,  240 

reserve,  246 

residual,  246 

tidal,  245 
Voluntary  striated  muscle  tissue, 

117 
Vomer,  66 
Vulva  of  vagina,  417 


Waste  products,  elimination  by 
skin.  323,  328 
in  sweat,  328 
in  urine,  319,  321 
Water  in  body,  25 
Wharton's  duct,  258 
White  fibrous  tissue,  48 

cells    of    blood.     See    Corpus- 
cles, 220 
Windpipe.     See  Trachea,  238 
Wirsung's  duct,  301 
Wrisberg,    cartilage    of    (larynx), 

236 
Wrist,  bones  of,  90 


Yellow   body    (corpus   luteum), 
426 


INDEX 


483 


Yellow  elastic  tissue,  48 

spot  of  retina  (macula  lutea), 
402 
Yolk,      formatitive,     ovum,     of 
35 
nutritive,  35 


Z 


Zona  pellucida,  425 
Zygomatic  process,  63 
Zygomaticus  major  muscle,    129 
minor  muscle,  129 


^    fc> 


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